President Carter asked Congress yesterday to make a series of offsetting changes in the food stamp program under which some people would be moved off the rolls while others would move on, and the cost would stay about the same.

The main beneficiaries would be people - an estimated 2.5 million to 3 million - who are eligible for food stamps today but cannot raise the cash required each month to "buy" the coupons.

Under the Carter proposal, recipients would not longer have to put up cash. A family today might be required to put up $100 in cash for $166 in stamps, for a "bonus" of $66. Carter would simply give that family $66 in stamps.

To pay the cost of adding families to the rolls this way, Carter urged changes that would knock off the rolls about 1.5 million persons with income significantly in excess of the federal poverty level.

These changes are complicated, but a family of four would no longer be able to qualify for stamps if its income was much over $8,000 a year. Under current law some families with higher incomes qualify, if they have unusually high medical or other living expenses. These higher-income recipients have become a symbol to critics of the food stamp program.

Food stamps in the last 10 years have become one of the largest of the federal governments welfare programs. Currently about 17.3 million individuals receive the coupons, or roughly one American out of 13. The annual cost is about $5.5 billion.

Agriculture Secretary Bob Bergland, in presenting Carter's proposal to the House Agriculture Committee yesterday, warned that the President is committed to holding costs at present levels, and quoted the President as having said a bill with higher costs would be unacceptable.

Carter did not approve the stamp proposals until Monday afternoon. They are his first important proposals in the welfare field. The Department of Health, Education and Welfare is changes in the welfare laws, which Carter has promised to send Congress later this year.

The proposal met with a generally favorable response, especially from lawmakers and outside groups that have been pushing for the elimination of the purchase price provision.

"This is a strong signal to the Congress and the American people that the Carter administration is committed to an equitable reform of the stamp program." said Rep. Fred Richmond (D-N.Y.), chairman of the House Food Stamp subcommittee, who has introduced a similar measure himself.

However, Richmond warned that the proposal is still unacceptable to many lawmakers because it would shift too much food stamp aid from the Northeast and Midwest to the South. Particularly hard-hit would be the Northeast, accroding to Ron Pollock, director of the Washington-based Food Research Action Center, which has advocated revision of the food stamp program.

This regional shift would occur because of the method Carter has chosen to keep higher-income families off the rolls. A family's eligibility and the amount of benefits from the stamp program depends on its net income - total income minus certain deductions for certain living expenses.Currently these are itemized deduction of $80 plus a percentage of earnings in those families where someone works.

This change to a standard deduction would hurt some beneficiaries, and help others. In general, it would hurt regions where living costs - and current, itemized deductions - are high, and help those where costs are relatively low.

Thus, according to FRAC's figures, 49.2 per cent of current recipients in the Northeast would either be knocked off the rolls or have their benefits reduced, while the rest would either break even or come out slightly ahead.

In the Southeast, by contrast, only 22 per cent would lose and the rest would break even or gain.

The food stamp program will expire Sept. 30 unless Congress extends it. That extension is part of the pending revisions in basic farm legislation which the Agriculture committeeof both houses are considering.