The congressional system for determining national spending priorities, a creation of the partisan wars of the Nixon years, has weathered a new series of shocks from none other than the new Democratic administration in the White House.

The past three months have seen a series of adversary exchanges between Congress and the executive branch and castigations of the White House by the congressional budget committee chairman, Sen. Edmund S. Muskie (D-Maine) and Rep. Robert N. Giaimo (D-Conn.).

Congress created its own alternative budget process in 1974 in response to President Nixon's repeated challenges to the traditional congressional control of the purse. But in the opening months of the Carter administration the system has been threatened both by White House-Capitol Hill friction and also by intramural skirmishing between liberals, conservatives, Democrats and Republicans in Congress.

At one point in the budgetary political warfare Giaimo and Muskie accused the White House of lack of communication with congressional budget policymakers. At another, an odd coalition of House Republicans and liberal Democrats voted to repudiate the House Budget Committee, thereby jeopardizing the whole process.

And yet, as the first phase of the process nears completion, almost everyone in Congress - from the conservative, Republicans to the black caucus - agrees that both the independence and the integrity of the congressional budget game have been strengthened by this year's test.

"It's been a helluva job to maintain the independence of the congressional budget this year," Muskie said, "but we've done it."

"The question was whether we were going to be a rubber stamp or work out our own priorities," Giaimo remarked. "I think we've answered that question."

The best evidence for that assertion lies in the fact that, for the first time since the congressional budget process began, some House Republicans have overcome their suspicion and have joined in shaping and defending the spending resolution. House Minority Leader John J. Rhodes (Ariz.) said there has been a "crack in the wall" of solid GOP opposition to the procedure.

The Senate passed the resolution setting a $460.9 billion spending target for fiscal 1973, beginning next October, by a comfortable 54-to-22 margain on Friday. Barring upset, the House will stamp its approval on the same figure on Tuesday.

The spending is $1.6 billion less than Carter has proposed. But because the President anticipates higher revenues than the congressional budgeteers, his budget shows a $7 billion smaller deficit than theirs.

"There's not that much difference," said Bert Lance, the director of the Office of Management and Budget, "and over the balance of the year, I think we can move even closer together."

That benign blessing on Congress' handiwork belies the series of shocks the administration handed the congressional budget-makers along the way.

The first was the decision by Carter, soon after his election, to add an economic stimulus package to the fiscal 1977 budget already approved by Congress.

That proposal was thoroughly discussed with congressional Democrats and widely approved by them, even though it meant Congress would have to do something it had never done before - reopen its agreed-upon budget for the current fiscal year and make a substantial alteration.

But on April 13, when Carter decided to withdraw the $50-a-person rebate that was at the heart of his stimulus program, there was no consultation and little advance warning to those same Democrats.

Muskie summoned Lance and other top Carter economic advisers before his Budget Committee and berated them for scuttling the centerpiece of the budget. Sen. Henry L. Bellmon (Okal.) ranking Republican on the committee and a full partner with Muskie in its direction, told Lance that Congress had gone out of its way "to accommodate a new President" only to be left "with egg on its face."

Muskie insisted that the revenue estimates in the Senate budget resolution be left unchanged, as a way of demonstrating to Carter that the Congress would not automatically bend to every shifting signal from the White House.

But Muskie's troubles were minor compared to those Giaimo, in his first year as House Budget Committee chairman, faced when the House took up the budget resolution. The Senate had given the administration the $120 billion in defense spending authority it had asked. But the liberal majority on Giaimo's committee had recommended on $116 billion for the Pentagon.

On the House floor, defense advocates, backed by phone calls from Defense Secretary Harold Brown, added $4 billion to the Pentagon figure. Giaimo said that broke "the delicate balance between defense and domestic spending." Liberal Democrats angry about the Pentagon victory joined with conservative Republicans upset about the overall projected deficit and scuttled the whole budget resolutions, 320-84.

It was, as many key members of Congress said in interviews last week, an important "learning experience" for a lot of people, starting with Jimmy Carter.

At a meeting in the White House on May 2, called to review fiscal policy problems between the administration and Congress, Carter apologized for his own and his colleagues' unknowing and unwitting collisions with the congressional budget process.

Reportedly he said in the room what Budget Director Lance has said publicly: "I've learned first-hand these last few weeks that this is still a young and tender process and needs to be brought along."

The House has been much more partisan - and difficult. From the beginning, Republican leaders feared Democrats intended to use the process to legitimize big spending and massive social programs. They stacked the budget committee with strongly conservative members.

On the other hand, many Democratic liberals feared the budget process would put clamps on those same programs, and have shied away from supporting it. To reassure them, more liberals were added to the Democratic side of the committee this year.

The result has been a sharp partisan division that has caused all but a handful of House Republicans to refuse ever to cast a vote for the budget resolution.

But the effect of the Republican boycott has been to give disproportionate power to the liberal Democrats in the bargaining over budget priorities.

As Giaimo told his Senate counterparts, "I know what I have to do to get the votes. I cannot get any from my colleagues on the right (the Republicans) . . . I have to come back with something to appeal to the majority of Democrats. Fifty-three per cent of the Democrats have been in the House four years or less. They are not World-War II veterans. They don't think the word from the Pentagon is gospel."

Giaimo made that statement during last week's House-Senate conference on the budget resolution. It was deadlocked for three days of heated debate over the $3 billion gap between the House and Senate figures on the defense budget, before agreeing on a $118.5 billion Pentagon target, which almost split the difference between the higher Senate and lower House figures.

In the course of that protracted controversy, Republican attitudes began to shift. For the first time, three conservative Republicans - Sen. [PARAGRAPH ILLEGIBLE]

That same message has been [WORD ILLEGIBLE] on the Republicans by such [WORD ILLEGIBLE] people as House Speaker [WORD ILLEGIBLE] P. (Tip) O'Neill Jr. (D-Mass.) and Ford administration budget chief[WORDS ILLEGIBLE] Lynn.

And the message appears to have been heeded. House Minority Leader Rhodes said, "I hope there will be more cooperation from now on," and some GOP sources predict there may be as many as 40 Republican votes for the budget resolution when it comes to the House floor Tuesday.

Regula, one of the Republican converts, said he sees the travails of the last two weeks "not as evidence of the weakness of the process, but as evidence of its strength. We faced up to it and fought the battles over spending targets."

Interestingly, the words of that Republican are almost identical to those of Rep. Parren Mitchell (D-Md.), a leader of the black caucus.

Mitchell said one benefit of the spring budget battles has been to give Carter "a loud and clear signal that it's our budget process and they would do well to keep their hands off. I'm glad the House had to go through this," he said. "It guarantees we'll not be a rubber stamp for anybody."

In addition, he said, the pitched battle over defense vs. domestic spending "forced the Budget Committee to prioritize." Although failing to gain some of his own social-program priorities, Mitchell warned fellow liberals that "if we destroy the budget process . . . every act in this House will be geared to defense and reducing the deficit."

From all these comments emerge some conclusions:

Widespread fears about the Democratic Congress letting a President of its own party co-opt its new budget process have been proved unfounded;

That process has gained broader Republican support in Congress than it ever previously enjoyed;

And Jimmy Carter, by treating the process with less than reverential respect, may inadvertently have provided just the test of strength it needed at this stage of its development.