In a dramatic display of political muscle, the National Women's Conference opened today with ceremonies featuring the First Lady and two predecessors, an array of top women government officials and the support of some of the largest mainstream women's groups.

This bipartisan blessing lent significance to what otherwise would have been a largely ceremonial event, albeit a loud and emotional one. Thousands of delegates, alternates and observers nearly filled the 6,000-seat Houston Coliseum this morning, cheering and chanting "ERA, ERA" at every opportunity.

Today's session was devoted largely to enthusiastic demonstrations of a unified belief in the need to demand equality for women. Cheers boomed out as the symbolic torch that women runners had relayed 2,600 miles from Seneca Falls, N.Y. - site of the first American women's rights meeting in 1848 - to Houston was brought into the hall. It was preceded by a marching band of young women in red-plumed helmets and a Girl Scout color guard leading the recitation of the Pledge of Allegiance. The torch was carried up to the stage, where First Lady Rosalyn Carter joined former First Ladies Betty Ford and Lady Bird Johnson as well as national figures such as Coretta Scott King and Rep. Barbara Jordan in a show of support. It was the first time the three Presidents' wives had shared the same stage in support of one goal.

Later, signs of disagreement among the delegates on the issues began to surface, underscored by the delegations from several states that opposed the existence of the meeting. Some refused to join any demonstrations of support, even one condemning "pornography for profit."

But Carter's message was that her husband's "concern about the outcome of your agenda is deep."

"I am proud to be a part of the National Women's Conference," she said. "Never before in our history has there been such a women's meeting - in numbers, in preparation, in diversity, in long-range effect. The breadth of opinion, ethnic groups, income and occupation represented here is remarkably reflective in our whole country."

Her words were particularly significant because opponents of the $5 million federally funded conference are claiming that it does not represent American women, while supporters are trying to convince the public and Congress that it does.

The conference is designed to identify barriers to women's equality and produce recommendations to eliminate them. These recommendations, which include such things as federally funded child care, "reproductive freedom" and the creation of a Cabinet-lievel women's department, are to be sent to President Carter.

But the primary message that participants here clearly wished to send to the rest of the country was that they represent a broad-based support for equality, including the ERA, that encompasses women all over the country.

"Human rights apply equally to Soviet dissidents, Chilean peasants and American women," said Jordan (D-Tex.) in her keynote address.

Former White House assistant Jill Ruckelshaus asked the women to stand, hold hands and recite a pledge. "We are here, America. . . We seek liberty and justice for all. . . And this time, America, we will not be denied."

Government support of this meeting goes beyond the $5 million appropriation and the presence of the First Ladies. Nearly every federal department in Washington has sent a woman official here or detached a woman employee to serve on the conference staff during the past month.

Other examples include the Department of Transportation, which has given $25,000 to the conference because transportation will be discussed, and the Johnson Space Center near Houston, which has sent high-speed printing equipment to be used here.

This support has been the target for opponents of the meeting, who object to "taxpayers' money" being spent on the conference to talk about "killing babies and lesbian rights," as one of them put it. Even as the delegates were meeting today, a rally of antiabortion, anti-ERA and anticonference groups was being held across town at the Astro-arena.

The opposition charges that the conference is "antifamily," which led to presiding officer Bella Abzug making a point of introducing the 40 members of the International Women's Year commission by noting that "among us we have 74 children."

Abzug was later introduced in a speech that included the information that she has been married to Martin Abzug for 33 years, and at another point the women in the audience were asked to raise their hands if they are homemakers. More than two-thirds did.

Liz Carpenter, an IWY commissioner and former press secretary for Mrs. Johnson, introduced 12 delegates from the stage and recited a litany of the diversity of the women involved in the deliverations:

"Here is 85-year-old Clara M. Beyer of Washington, D.C.," Carpenter said, "retired government worker of 60 years, protege of Justice [Felix] Frankfurter . . . mother of three sons and 12 grandchildren); the delegate from Illinois, Marge Jinrich - 14 years with the United Auto Workers - she helps support her semi-invalid husband and five children on a paycheck of $8,500; from Minnesota, . . . Mary Ann Brueschoff, who runs her own poultry farm - she was butchering geese when I called (her) . . .

Later, as the meeting began its business session, a glimpse of the conflicts between the largely pro-ERA assemblage and a minority group of opposition delegates flared briefly. The legitimacy of the Mississpipi delegation was challenged by a delegate from Pennsylvania because it is all-white even though the state has a large black population, and because the five male members of the group allegedly belong to the Ku Klux Klan. As other delegates loudly booed the Mississippi group and gestured thumbs-down, presiding officer Ruth C. Clusen, head of the League of Women Voters, denied the challenge.

Delegate Norma Temple, whose husband, William, is also a Mississippi delegate, said that none of the male delegates belongs to the Klan although one delegate's husband does.

Without significant dissent, the first three items of the Action Plan were approved by the convention, which began to get down to business by mid-afternoon. The proposals deal with the arts and humanities, battered women and business (See Page A28). The issues were being dealt with in alphabetical order.