House Democratic leaders, in a subtle bit of parliamentary maneuvering, have removed all legislative road-blocks to the first big pay raise in eight years for members of Congress and other high-ranking federal officials.

Coupled with Senate approval of the pay proposal on Wednesday, the leadership action means that the pay proposal apparently will become law on Feb. 20. The only way to pay raise can be stopped is by a negative vote by the House or the Senate before that date. Otherwise, it automatically goes into effect.

The proposal would raise congressional salaries from $44,600 to $57,500 and contains similar increases for judges. Cabinet officers and top civil servants. More than 22,000 people would benefit directly or indirectly.

The House Democratic leaders, who favor the pay increase, feared that House members would kill it rather than face the political backlash of a vote for it.

So the leaders referred the pay raise issue to the Post Office and Civil Service Committee. The committee, in turn, referred it to an ad hoc subcommittee headed by Rep. William D. Ford (D-Mich.) for three days of hearings next Monday through Wednesday.

The House then goes on a Lincoln Day recess until Feb. 16.

The full committee is expected to meet on the pay issue the day the House returns to work. But under House rules no measure approved by a committee can be taken up by the House until three days after a committee report on the measure has been printed. In the unlikely event the committee approved a resolution of disapproval of the pay raise, it couldn't be put to a House vote until after the 19th - when it would be too late.

There is no time to pull the disapproval resolution out of committee by a discharge petition and no way for a member to call it up for a House vote until it has been approved by committee.

It appears that the only way opponents could get a House vote on the pay issue would be with the help of the House Rules Committee - which is controlled by the Democratic leadership.

Opponents concede they have little chance of stopping the pay raise, but they have been pouring out press release denouncing this "devious" procedure by which Congress can get a pay raise without voting for it.

New members are especially sensitive about going home for the Lincoln Day recess and being asked how come the only thing they have done since going to Congress was to accept a 29 per cent pay raise when the national need was belt-tightening.

It was because voting to raise their pay was such a painful political experience that Congress in 1967 set up the present procedure. Every four years a commission makes pay proposals for top government officials to the President, who then sends his recommendations to Congress. They take effect unless disapproved by either house of Congress within 30 days.

This worked in 1969 and raised congressional pay from $30,000 o $42,500. But the Senate killed the next round of pay raises in 1974 and the top layer of government officials has had only a 5 per cent pay raise - which slipped through last year - since 1969.

Meanwhile the cost of living has gone up by two-thirds and many top officials are leaving government service and their jobs going begging.

President Ford urged that the House and Senate enact strong codes of conduct for themselves to accompany the pay raise. Committees are at work drafting codes but adoption will lag behind the pay raises.

Bills have been introduced in the House to defer the congressional pay raise until the next Congress or until the codes of ethics are adopted. Rep. Larry Pressler (R-S.D.) has asked the Supreme Court to declare unconstitutional the procedure by which members of Congress can get a pray raise without voting for it. A three-judge court here ruled against him.

House Minority Leader John J. Rhodes (R-Ariz.) has called for a House vote on the pay raise. Any other course would be "cowardly and wrong," he said. Rep. Ford, who favors the pay raise, has invited all members of the House to testify at his hearings next week. Any member who feels it necessary to get on the record on such as issue can do it with testimony, Ford said.