When the Democratic National Committee meets today to approve automatic delegate status at the 1984 convention for at least three-fifths of the Democratic members of the House and Senate, it will mark a major change in its presidential nominating process. After a dozen years of unceasing efforts to increase grass-roots control of the convention, the party is inviting the professionals to reassert their power.

It will also be a moment of personal victory for a little-known member of the House, who has achieved increasing influence through the unusual process of serving as a liaison between Congress and the party organization.

Rep. Geraldine A. Ferraro (D-N.Y.), the 46-year-old second-termer from Forest Hills, was the negotiator of the deal for congressional representation that prevailed in the party's latest rules revision commission and will be ratified by the national committee.

Ferraro, who serves as the secretary of the House Democratic Caucus, had lots of help in cutting the deal. Democratic National Chairman Charles T. Manatt promised such participation when he was seeking his office a year ago. And the commission chairman, North Carolina Gov. James B. Hunt Jr., made it a top priority of his own.

But Mark Siegel, the veteran Democratic operative who helped draft "the Ferraro plan," said her sponsorship was a key to its success.

"It came from the right person," Siegel said. "She is a bridge between the new and old politics and between the feminists and the organization Democrats. And she's tough enough to take them all on."

In the crucial debate of the Hunt Commission, Ferraro had to do just that. She found her plan under attack from state Rep. Cleta Deatherage of Oklahoma, a feminist who argued that bringing in so many male congressmen would dilute the power of women, and from New York Democratic Chairman Dominic J. Baranello, who saw the congressional caucus selection as an infringement on the power of state parties.

Ferraro held her ground in the spirited debate--and the deal was ratified.

Her role is an unusual one, because most members of Congress find a lot of reasons--or excuses--to keep their distance from internal party politics. Of the four other members of Congress appointed to the Hunt Commission, one was a complete absentee and the other three only occasional visitors.

Ferraro was at every session, as she has been at meetings of the party's strategy council, its training academy and its women's caucus from Baltimore to Des Moines.

What makes it all the more remarkable is that she says "I didn't start out as an organization person at all." Ferraro and her husband have three children and when the youngest was 8 in 1974, she moved from a private law practice to a job in the New York district attorney's office.

When the incumbent in her Queens-Long Island congressional district retired in 1978, Ferraro ran for the nomination and beat the party-endorsed candidate. It is a conservative, blue-collar district, including the neighborhood where the exterior scenes of Archie Bunker's house in the old TV series "All in the Family" were filmed. It regularly goes Republican in presidential races.

Ferraro won by stressing her credentials as a prosecutor, building strong support among the elderly and balancing her pro-choice position on abortion with support for tuition tax credits for private schools.

From the beginning, she took an approach to party politics unusual for today's generation of House members.

"She's done something unique," said Cliff Wilson, a New York assemblyman and district leader, who did not support Ferraro in her first primary. "As soon as she was nominated, she reached out to the party organization. She made it clear that she would be a nationally oriented congresswoman, but wanted to relate to the needs of the district--not by building a separate structure of her own but by working with the party structure that exists.

"So every couple months, she has a formal meeting with the district leaders, the committeemen and the state and local elected officials and she spends a couple hours going over things. She brings Washington to us and we bring Albany and the district to her. She also spends a lot of time at functions in our clubs."

Ferraro took an unusual approach to the Washington end of her job, as well. Arriving in 1979, when many congressional Democrats were already washing their hands of the Carter administration, she decided to repay the help she had received in her campaign from President Carter's mother and several Cabinet members by trying to bridge the gap between the White House and Capitol Hill. She brought House colleagues to the homes of White House staff members for informal legislative strategy sessions and later attempted to enlist them in the 1980 Carter campaign.

"When he lost," she said, "I was really concerned about how to build up the Democratic party. A lot of people in Congress had been running against the party, because they felt they got no help from the party. But the idea of a single individual candidate all alone is behind us--you need a very strong party to govern this country."

Ferraro sought the largely honorific post of caucus secretary, in part, she said, "because there are not many spots in the House hierarchy where a woman can be heard." She used it to gain a place on the House Democratic Steering and Policy Committee and then began showing up at national party meetings to represent House Democrats.

Negotiating delegate seats at the 1984 convention was her biggest task, but now she is working on the policy panels for the mid-term convention in June in Philadelphia and lining up congressional participation.

What's in it for her? "I'd like to make it to some sort of leadership position in the House," she said, "but if a Senate seat becomes available . . . ."

Ferraro tried for a vacancy on Ways and Means last year and lost, in part because New York already had three seats on the committee. Now she has her eye on the Rules Committee vacancy that will be created by the retirement of Rep. Shirley Chisholm (D-N.Y.).

"I don't want to get a label as a pushy broad," she said, "but I'm not a kid either. I want to be part of what the Democrats put back together."