More than 40,000 shouting and clapping supporters of Equal Rights Amendment, many dressed in the traditional white of the Suffragette movement, marched down the Mall to the Capitol yesterday to exhort Congress to give the States seven more years to ratify the amendment.

They marched despite a hot, hazy, breezeless afternoon with temperatures hanging in the low 90s.

The organizers of the tightly discipline march proclaimed it the "largest parade for feminism in history."

Their purpose is to gain additional time to persuade at least three state legislatures to approve the Equal Rights Amendment. A deadline set by Congress calls for the amendment to die next March unless more time is granted. The supporters of ERA say they cannot get the necessary votes in the next nine months.

The theme of the demonstration was sounded again and again in dozens of short, emotional speeches.

"We need an extension of time to fight the lies about the Equal Rights Amendment," said Rep. Elizabeth Holtzman (D-N.Y.). ". . . It is a fulfillment of the American dream and not a threat to anyone . . . Time is on our side and we will win."

Organizers vowed to besiege members of Congress at their offices today. "We must not leave Washington . . . yes or no, from every member of this body," declared Patsy Mink, president of Americans for Democratic Action and a former congresswoman from Hawaii. "And if they dare to turn us down . . . we will turn them out on the next election day."

Presidential aide Midge Costanza told the crowd she had brought them a message of support from her boss, immediately prompting a mixture of moderate applause and wide spread boos and cries of "Where is he?"

But later Costanza won an ovation with an attack on anti-ERA leader Phyllis Schafly. "There is a woman in this country who does not want her rights and who has become a spokesman for women who do not want theirs," said Costanza. "Our message for you, Phyllis Schafly, is that we paid for this ourselves. We wish you could say the same thing."

Schafly had charged earlier yesterday, on the ABC-TV news program "Issues and Answers," that ERA demonstrators were "the same crowd who went down to Houston last November (for the National Women's year Conference), a combination of federal employes and radicals and lesbians who spent $5 billion of our tax payers' money. . ."

Eleanor Smeal, president of the National Organization for Women, which put together yesterday's rally, said it had been financed by contributions from more than 300 organizations, including unions and educational, church and women's groups.

Demonstrators began gathering on the Mall, near 14th Street, at about 9 a.m. yesterday, with each of the hundreds of delegations meeting under its own purple, yellow and white banner. Marching out onto 14th Street at noon, the procession had the look of a huge army advancing into battle.

Alongside the National Archives building at 8th Street and Constitution Avenue NW, the marchers paused to applaud a group standing on the archives steps with a banner bearing the amendments full text: "Equality of rights under the law shall not be denied or abridged by the United States or by any state on account of sex."

"ERA now!" was the chant most often repeated by the marchers, but at other times they shouted, "One two three four, we need three more (three more states to ratify), five six seven eight, Congress must extend the date!"

When the front of the column reached the Capitol half an hour later, there was a continuous line of marchers all the way back to 14th Street and Constitution Avenue, and a few thousand were still waiting patiently in neat rows to leave the Mall.

Almost to a woman - men composed a substantial minority of the throng - participants refused to be downcast about prospects for ERA's ratification. Thus far, 35 states have voted to ratify the amendment, but only Indiana has voted for ratifications since 1976. In that time, three state legislatures - Idaho, Nibraska and Tennessee - have reversed earlier ratification votes.

The amendment needs the approval of three more legislatures in order to become part of the Constitution. Supporters concede that this will not occur before the deadline set by congress of March 22, 1979. ERA backers are trying to get Congress to approve a seven-year extension for state ratification until 1986.

"Everybody's for it but we don't have it," said Bella Abzug, former congresswoman from New York and now cochairwoman of the National Advisory Commission on Women. "They have allowed a highly organized minority to stop the will to a majority. We assumed that we would have it without difficultly and that was a mistake."

Rank-and-file demonstrators echoed the speaker's expressions of faith in ERA's ultimate victory. "Even if we have to start again and get the whole 38 states again, it is going to come," said Marilyn Boll, a public relations executive from Washington.

"I don't think anybody that's here is discouraged," said Mary Jane Smart, a retired government worker who was on crutches yesterday because "I whacked my knee on a doorsill."

One of the most demonstrative of yesterday's demonstrators was Marcia Karlin, a painter and photographer from Guilford, Conn. "I was born a feminist," said Karlin. "I came out of the womb with a clenched fist."

Where's Shirley Chisolm? Where's Barbara Jordan?" Karklin shouted insistenly at a group of celebrities gathered on a podium. "Where's Eartha Kitt? Where's Gloria Steinem?"

"I'm here," replied Steinem, seated a few yards away.

"No kidding, your're Gloria Steinem?" said Karklin."I saw you in Philadelphia. You look different."

A few minutes later, Steinem, editor of Mr. magazine, told the crowd that "the lawful and peaceful stage of our revolution may be over. It's up to the legislators. We can become radical, if interfere with the ratification of the ERA, they will find every form of civil disobedience possible in every state of the country.

"We are the women our parents warned us about, and we're proud," said Steinem to loud cries of approval.

March organizers periodically revised their estimates of the crowd's size, from 35,000 in the early afternoon to 90,000 by the time the rally was at full strength.

The commander of the U.S. Park Police demonstration unit put the figure at 90,000 to 100,000 - based on "years of experience," according to a spokesman - but three other police estimates were in the range of 40,000 to 55,000.

A Park Police officer abroad a helicopter said the crowd appeared to number about 50,000 at 4 p.m. D.C. police offered a lower figure of 40,000 based on "educated guesswork," and Capitol Police put the number at 55,000.