President Carter sent Congress his first reorganization plan yesterday - a proposal he said would cut the size of the White House staff by 28 per cent and improve the efficiency and quality of presidential decision-making.

In a brief appearance in the White House press room. Carter said the restructuring of the Executive Office of the President would serve as "a model for a very aggresive effort" to fulfill his campaign plege to reorganize the entire executive branch.

According to White House figures, the plan will reduce the number of full-time White House positions from 485 to 351 and scale back the executive office of the President, which embraces the White House and 18 satellite units, from 1,712 to 1,459 positions.

The White House cutback comes very close to Carter's previously declared goal of reducing his own immediate staff by 30 per cent. The planned reduction in the entire executive office amounts to 15 per cent.

Officials said that while one-third of the jebs will be transferred to other parts of the government, the plan should produce net savings of $6 million a year.

All affected individuals will be offered other government jobs. Bert Lance, the director of the Office of Management and Budget, told a White House briefing.

The plan - the first submitted under reorganization power granted Carter earlier this year - will go into effect unless vetoed by the House or Senate within 60 days.

Initial reaction of Capitol Hill indicated there will be no serious objections to the proposal.

Hearings are expected to begin within two weeks. While Carter expressed satisfaction that his reorganization team, headed by A.D. Frazier of the White House and Harrison Welford of OMB, had been able to achieve what he called "very severe" cutbacks, he and his aides put heavier emphasis on the expected improvements in the policy-making and administrative processes of the White House.

Carter said the "basic thrust" of the changes is "to strengthen Cabinet government" and to assure him a "free flow of information and advice from diverse sources."

Others emphasized that the chances - principally affecting domestic and economic policy planning - are designed to plug three major gaps in the white House staff system that emerged during the review.

The study showed a need for closer and more formal examination of alternative policy proposals, greater emphasis on overall political strategy, and better follow-up measures to assure that presidential decisions are being carried out by the departments.

Among the major changes Carter has ordered are:

Giving his domestic policy assistant, Stuart Eizenstat, responsibility for managing a more formalized system to analize domestic and economic issues, modeled on that now used by the National Security Council for international issues.

Asking Vice President Mondale to head a committee of senior presidential assistants charged with setting priorities among issues and fixing a timetable for their consideration.

Consolidating two separate White House "paper flow" system into one system run by staff secretary Rick Hutcheson.

And giving Jack H. Watson Jr., the secretary to the Cabinet, responsibility for long-term follow-up on presidential decisions.

The sources said the plan also envisages an enlarged role for presidential assistant Hamilton Jordan, as the chief supplier of political perspectives on emerging issues.

In mechanical terms, Carter's plan calls for abolition of seven of the 19 units that comprised the executive Office of the President when he succeeded President Ford.

They are the Office of Drug Abuse Policy, the Office of Telecommunications Policy, the Council on International Economic Policy, the Federal Property Council, the Energy Resources Council, the Economic Opportunity Council and the Domestic Council. Two other units - the Economic Opportunity Council - already have been disbanded.

The other units proposed for extension - the Council on Environmental Quality and the Office of Science and Technology Policy - were spared by Carter, although some of their functions and staff will be shuttled to the departments. Carter's decision on these units forestalls potential congressional opposition ot the reorganization plan.

The President also decided to retain the Council on Wage-Price Stability, the chief arm in his effort to contain inflation. But instead of having a 13-member staff of its own, officials said it would use the staff of the Council of Economic Advisers, which itself is being reduced in size.

Also spared by presidential decision were four aides with special personal ties or constituences: Peter G. Bourne, a public health specialist and early political supporter: Greg Schneiders, Carter's personal assistant during the campaign; and Joseph W. Aragon and Martha M. (Bunny) Mitchell, respectively the top-ranked Mexican-American and black members of the White House staff.

Most of the functions of the abolished units would be transfered elsewhere in government, and Lance conceded that the projected personnel and cost savings are only estimates.

For example, Frazier said that of the 134 White House staff position being abolished, 70 would simply be transfered to a new central administrative unit in the Executive Office of the President.