THE ADMINISTRATION has struck a considerably more conciliatory tone than it sounded a year ago, but when you get down to the budget details, the differences from last year's budget are far less marked.

One major difference is that, thanks to the Social Security commission, the administration can present a credible program for tiding Social Security over its near-term financial difficulties. That compromise has given administration planners a good excuse for proposing a temporary freeze on federal civilian pay and on cost-of-living adjustments in other entitlement programs. If Congress will go along with the freeze--which is hard to justify in cases such as food stamps--it will produce hard savings of several billion dollars.

The administration has also put flesh on its long- promised proposals for curbing Medicare costs. The changes won't be popular with either the medical professions or the elderly, but they represent a reasonable attempt to put some measure of control on this runaway program. It's worth noting, however, that as administration planners have become more familiar with the difficulties of medical cost control, they have scaled back expected savings from the $4 billion level that the administration claimed last year for its then unspecified program.

There is a good bit of unrealism in other claimed savings. The $9 billion to be saved in agriculture subsidies is an example. So is the sharp cutback in federal retirement benefits. Reform is needed here, but not on the scale proposed. And Congress isn't likely to go along with the plans for job training programs either. Some fancy budgetary footwork in administration summaries makes it look as though an increase were planned in this area. But in fact spending is scheduled for another drop.

The part of the budget least changed from last year deals with programs for the poor. Once again, these programs--welfare, nutrition, social and legal services and so on--are scheduled for substantial cuts in purchasing power. Leaving aside housing programs, which will continue spending for past commitments but will ultimately drop sharply, programs for the poor would buy 18 percent less than in 1981. Take account of the facts that unemployment has made more people eligible for these programs and that soaring medical costs have absorbed an ever greater part of the money available, and you will find that the average poor person already receives far less real help than he did a few years ago.

Essentially the new budget presents Congress with the same bleak prospect: having to persuade powerful middle-class lobbies to relinquish some part of their substantial interests in federal spending and requiring the poorest and least defended of the nation's citizens to give up a still larger share of their meager claims.