Delegates to the National Women's Conference voted to suspport a resolution approving of legal abortions late today, touching off an emotional demonstrataion by delegates opposed to abortion.

The controversial vote, which came after about 20 minutes of debate, had polarized those meeting here more than almost any other issue. Delegates opposed to abortion had been preparing strategy for days, although their leaders conceded they had little chance of success.

As cheering pro-abortion delegates rose to their feet to signal their approval, antiabortion forces waved protest signs. As soon as the result was clear, they rushed toward the stage, as if at a predetermined, signal, singing and unfurling banners.

As Chairperson Anne Saunier gaveled in vain for order, Por-abortion forces started singing "America the Beautiful" and chanting "Choice, Choice," while waving clenched fists.

During the brief debate, for which Saunier refquired an equal number of speakers for both sides, delegate Anne O'Donnell, a nurse from Michigan, told the gathering that "the promise of a women's movement will be destroyed if you go on record as approving this destructive resolution."

Two Missouri delegation members attacked abortion, but the so-called right-to-life forces were unable to execute an elaborately desingned floor strategy that had been hammered out in an overnight meeting that lasted until3 a.m. today.

The demonstration that followed the vote sparked a few instances of tugging and scuffling between delegates carrying banners of opposing viewpoints.

In all, the abortion issue consumed less than 30 minutes from proposal to demonstration, and the proceedings were carried out with a deliberate efort to make it appear that the nationally televised conference pursued its business fairly and with concern for tthe minority viewpoint.

Earlier, opponents of the Equal Rights Amendment, who number about 300 at this meeting, had claimed that parliamentary tactics had prevented them from voicing their views on the floor of the conference.

An effort to introduce a resolution opposing the ERA was ruled out of order Saturday night by presiding chairperson Mary Ann Krupsak, creating a flurry of complaints among the anti-ERA forces.

After an hour's debate punctuated by numerous demonstrations of support and minority opposition, the delegates voted overwhelmingly at midnight Saturday to urge passage of the ERA.

The voice came as no surprise, since most of the 1981 delegates and alternates meeting here to discuss women's issues came committed to the ERA and have made that commitment clear since the first moment of this four-day conference.

For many, infact, the ERA, vote was what they came for. Thirty five states would prohibit discrimination on the basis of sex, but three more states are needed before the amendment becomes part of the Constitution.Although 30 states ratified the ERA within a year of its introduction in 1972, efforts have since bogged down as three states voted to rscind their approval and Many ERA advocates view Saturday night's action as a symbol of renewed efforts to campaign for the passage of the ERA in six targeted states.

Amid the confusion over parliamentary rules that has characterized most of the two days of business meetings so far, Krupsak, the lieutenant governor of New York, ruled that the anti-ERA resolution was "dedective" because it lacked a clause stating what the resolution was.

"This is not a complete sentence." she said after having given Rosemary Thomson of Illinois a chance to rewrite the motion. This morning Krupsak said she had allowed Thomson, a delegate who heads the anti-ERA Eagle Forum in Illinois, to resubmit the improperly worded resolution against the improperly worded resolution against the advice of the professional parliamentarian hired by the conference to arbitrate such matters. "Their tactics (the anti-ERA forces) seem to be to accuseus of parliamentary dirty tricks," Krupsak said. "For all I know that was an intentionally defective resolution."

Thomson said it was "possible" that she had "inadvertently" left out the final clause of the resolution when she transferred her motion to the official forms, or that the hand-written words did not show through on the carbon copy. Nonetheless she charged that anti-ERA spokeswomen have been prevented from speaking and have been intentionally misinformed on procedure by conference officials.

"The problem is that most of us here are not parliamentary experts," she said, a view undoubtedly shared by delegates of all viewpoints, judging from the confusion over procedure that is often in evidence.

Opposition forces introduced substitute motions to nearly every issue discussed Saturday, and Thomson said they will continue to do so throughout the conference. "We represent a constituency and it is our responsibility to let their voice be heard," she said. Delegate Joan Gubbins, the minority floor leader, has said that if these tactics are not successful the alternative strategy is to "hold a press conference."

The only recommendation unanimously approved at the meeting so far was one urging that the Equal Credit Opportunity Act of 1974 be "vigorously" enforced.

In other action before Saturday's adjournment, the delegates debated and passed recommendations on education, including a call to add women's studies to state school systems' curriculums; employment, and a call for more women in elective office.

Late this afternoon the delegates approved a strongly worded resolution calling for efforts to improve living and working conditions for minority women who have suffered double discrimination. Approval was followed by an emotion-charged demonstration, with the singing of "We Shall Overcome" and the forming of human chains on the convention floor.

Earlier, former Republican national Committee Chairman Mary Louise Smith said that Republican women "have the responsibility to show that (Stop-ERA head) Phyllis Schlafly is not a role model for Republican women." Schlafly was a leader of a so-called "pro-family" rally here Saturday to protest the federally funded women's conference.

Former RNC co-chairman Elly Peterson, who is a delegate here and co-chair of ERAmerica, said that "we're coming out of this with a whole new breed of women" who are potential recruits for the Republican Party "if we just don't label them as misfits and oddballs." She was referring to remarks by a local GOP chairman at Saturday's pro-family rally.

The most controversial issues to be faced by this conference-abortion, sexual preference and the establishment of a Cabinet-level women's department-were not due to be discussed until the final hours of today's meeting. On Monday there will be a discussion of future plans and then adjournment.

The issues are among 26 in a proposed National Plan of Action that the conference will send to Congress. The conference was established and funded with $5 million by Congress with the mandate to identify barriers to equality and to propose methods of eliminating them.