THE BUDGET resolution that Congress has now passed does one important thing. It keeps the deficit, and the strain on the economy, from getting worse. In the fiscal year that ends next month, the deficit will probably be about $210 billion. The congressional resolution sets a deficit of $172 billion for next year -- movement in the right direction, if not by any very dramatic amount.

President Reagan keeps blaming the allegedly spendthrift Congress for its failures, as he describes it, to get the budget under control. But this resolution is wholly a congressional achievement, worked out by the leaders of the two houses with the most minimal assistance from the administration. The president's role this year has repeatedly made agreement more difficult and significant deficit reductions less likely. The greatest pressure for a real attack on the deficit has come consistently from the Senate -- most prominently from Sens. Robert J. Dole and Pete Domenici, the majority leader and the chairman of the Budget Committee, but with much support from many others including, let it be noted, some Democrats.

In April, Sens. Dole and Domenici worked out a compromise with Mr. Reagan that would have moved the deficit a little lower than the one in his original February budget proposal. But Mr. Reagan evidently decided that he didn't like that agreement, and in early July he swung around and undercut the senators by striking a different deal, at higher spending levels, with the House Democrats. The budget fell into deadlock for two weeks. The senators then attempted to move it forward again, toward lower deficits, by suggesting an oil import tax and postponement of a cost-of-living increase in Social Security benefits. Mr. Reagan had accepted a broader Social Security freeze in April, but renounced it in the July deal with the Democrats. Last Monday, he abruptly rejected the senators' offer.

With that, the Senate and House put together their own resolution. As Sen. Domenici said, it was "the best that we could do under the circumstances." You might want to note that, with the active and vigorous collaboration of the Democrats, it sets spending and deficit limits that are slightly but noticeably tighter than those Mr. Reagan proposed at the beginning of the process in February.

The budget process is far from complete. The resolution is only a guide for legislation still to be enacted -- the most contentious of which will be the farm bill. The resolution calls for a cut of one- fourth in farm spending next year, while the agriculture committees in both houses seem to be moving in the opposite direction.

But with all of the qualifications, the resolution represents an improvement over the first draft that Mr. Reagan sent to the Capitol six months ago. It does as much as Congress can do, in the absence of a change of heart in the White House.