President Carter's first major foreign policy test with Congress, in Senate votes Thursday on troop withdrawals from South Korea, left his executive authority unimpaired, administration spokesman said yesterday.

At the same time, officials readily concede that Senate votes on a series of subjects this week resoundingly underscored the determination of Congress to participate in shaping foreign policy.

"It is not surprising," one administration planner said privately, that the Carter administration's "foreign policy initiatives are being questioned." He said, "A lot of people are used to 'old-think' in foreign policy," and he feared "this would come out much worse than it did."

Administration officials said they never wanted the test to endorse the President's plan to withdraw U.S. ground troops from South Korea in four to five years. It ended up Thursday in a struggle to beat down a repudiation of the President's policy.

Senate Majority Leader Robert C. Byrd (D-W.Va.), who led the fight to head off the challenge mounted by Senate Minority Leader Howard H. Baker Jr. (B-Tenn.) and other Republicans, told reporters yesterday:

"I think there was a message in the Senate's action . . . I don't think the White House will ignore the Senate's urging for regular consultation."

Byrd said "the mood of the Senate was such that the President would have been repudiated" if Bryd had not shifted the issue away from endorsement of the President's troop pullout plan. The key vote was on a motion by Sen. Bob Dole (R-Kan.) to recommit the bill, which was defeated 68 to 26.

The Byrd substitute said "U.S. policy toward Korea should continue to be arrived at by joint decision of the President and the Congress," with troop reductions "carried out in regular consultation with the Congress."

President Carter intends to proceed with the plan, in consultation with Congress, White House deputy press secretary Rex Granum said yesterday.

"There are certain decisions," however, Granum said, "on the deployment of military personnel that are the responsibility of the commander-in-chief, and he intends to carry out those responsibilities."

Similar emphasis was made at the State Department about the President's authority. Spokesman John H. Trattner said there will be "regular consultations with Congress on every phase of the plan to withdraw U.S. "ground forces from the Republic of Korea" - but "there are certain decisions to be made by the President alone" as commander-in-chief.

Administration officials said they are thankful they have weathered a series of votes this week involving Korea, Cuba, Vietnam and other departures in foreign policy, with what they regard as repairable damage.

"We took a pasting" in the Senate on Tuesday, an administration foreign policy specialist conceded. This was on a Vietnam-Laos-Cambodia amendment by Dole to penalize them for "gross violation" of human rights.

Dole's amendment to a bill authorizing $5.1 billion for world lending agencies directed U.S. representatives to vote against any aid for the Indochina Communist nations. It would cut U.S. aid to those agencies if they voted such loans over American objections.

President Carter appealed to both houses of Congress not to tie the administration's hands in the lending agencies and deprive it of flexibility to use its votes as leverage "to release prisoners or stop other offensive practices . . ."

In the House yesterday the administration won a vote to help its chances for blocking restricted legislation on loans nations that consistently violate human rights.

By a vote of 200 to 161, the House voted against binding its conferees in advance to stiff human rights terms in international lending agencies.

During Senate voting Thursday on the legislation involving U.S. troops in South Korea, tied to a $1.6 billion State Department authorization bill, the Carter administration escaped another restriction on its foreign policy initiatives, in Cuba.

That rejected amendment, also by Dole, was aimed at putting the Senate on record in opposition to moving further toward U.S. diplomatic recognition of Cuba. It would have stipulated the price of recognition to be full compensation for all expropriated American property in Cuba, and withdrawal of all Cuban troops from Africa.

These kinds of challenges produced in the Senate what one administration official described as "a partisan clash of an intensity I have not seen in some time."

The State Department's chief for congressional liaison, Douglas J. Bernet Jr., a recently arrived Senate staff veteran, yesterday expressed an undismayed outlook on the problem:

"Congress has once again asserted its desire to be informed, to participate in major processes of policy . . . From my personal point of view, I think it's extremely welcome when there are such big foreign policy issues being thrashed out . . ." In the end, Bennet said, "foreign policy is likely to be better if you have active congressional participation."