The Democratic Party's rule makers reversed a decade of increasing grass-roots control of their presidential nominating conventions last night and voted to give about 550 votes at the 1984 convention to uncommitted elected and party officials.

By a 47-to-6 vote, the commission on presidential nominations, headed by North Carolina Gov. James B. Hunt Jr., set aside those seats for members of Congress, governors, big-city mayors and other elected officials and party big-shots.

They would be freed from the requirement the other 3,300 Democratic delegates face to state a candidate preference, and they would not be bound by the results of primaries or caucuses in their own states.

The decision, taken just before midnight after four hours of sometimes heated debate, represented a major turnaround from the trend of the Democratic Party for the last 12 years. During that time, the Democratic delegate selection was increasingly controlled by presidential primaries and caucuses open to any and all party members.

Last night's vote was a major victory for Hunt, Party Chairman Charles T. Manatt, and leaders of Congress and organized labor--all of whom claimed that recent Democratic conventions were out of touch with mainstream party thinking, because they were dominated by issue activists and elected officials didn't have enough influence.

Some women members of the Hunt commission tried in vain to require that half the uncommitted delegates at the 1984 convention be women, but they were beaten on the issue, 42 to 14.

However, the 1980 rule that the entire convention membership be balanced between men and women was reaffirmed. That will require states to select more women than men among the committed delegates.

The new rule was offered by Rep. Geraldine A. Ferraro (D-N.Y.), the secretary of the House Democratic Caucus. It was strongly endorsed by Sen. Patrick J. Leahy (D-Vt.) and was supported also by close associates of former vice president Walter F. Mondale and Sen. Edward M. Kennedy (D-Mass.).

Leaders of Congress and organized labor had originally sought to have 30 percent of the 1984 convention seats reserved for the uncommitted elected and party officials, but that figure was resisted by party "reform" groups and by Kennedy's spokesmen. Ferraro said that her proposal, which would give about 14 percent of the votes to uncommitted delegates, was a compromise that would make the 1984 convention "flexible" but still prevent what she called "a brokered convention" where the nomination could be settled in back-room trading.

The new rule allows the House and Senate Democratic caucuses to pick two-thirds of their members as delegates. Ferraro accepted an amendment that would require the caucuses to solicit recommendations from state Democratic committees, after the commission rejected efforts to give the states either selection or veto power.

The Hunt commission continues its work today and Saturday, and the rules must be ratified by the Democratic National Committee before they take effect for 1984.

Earlier yesterday, Rep. James R. Jones (D-Okla.), chairman of the House Budget Committee, told the party's executive committee he expected fewer defections by Democrats to support President Reagan's budget cuts than last year.

Warning that "some social programs" will be cut further in 1982, Jones said "the number of Democrats voting down the line for Reagan's cuts will be smaller," because many conservative Democrats "cannot tolerate" deficits of the size Reagan's budget is expected to include.

Jones said he believes there will be an economic upturn by midyear but fears it will be aborted by high deficits and high interest rates.

At its meeting, the executive committee approved rules for the party's midterm conference that minimize the possibility of any divisive issues debate. The rules for the meeting, to be held June 25-27 in Philadelphia, will confine discussion on seven broad policy topics to seven separate panels.

Each panel will report its "consensus position" and any other views that draw at least 25 percent of its members' votes in a consolidated statement to the closing plenary session. But the only vote in that session will be to accept the panel reports.