The peace treaty with Israel will be put before the Egyptian people in a referendum on April 19, President Anwar Sadat announced tonight.

On the same ballot, the Egyptians will be asked to approve governmental reforms and constitutional changes aimed at establishing Sadat's unique vision of "family" democracy.

Sadat is assured of overwhelming apprvoal of both the treaty and the governmental changes, probably by the margin of more than 90 percent he has gained on referendum in the past. That will show his Arab critics, he said, that the people of Egypt support his policy of peace and are ready to "start" a new era with new traditions."

The referendum on the treaty is not a constitutional requirement.

The Egyptian People's Assembly gave final approval to the treaty Tuesday night by a vote of 329 to 13 and Sadat is now legally authorized to exchange the instruments of ratification with the Iraelis at ceremonies scheduled for April 22.

Sadat, however, is under fire throughout the Arab world by critics who charge that he has betrayed the Arab cause and allege that he is not supported by the Egyptian people. The referendum will give him a tool to use in rebuttal.

In a televised address to the nation tonight, Sadat again flayed the other Arabs who have banded together to impose a political and economic boycott on Egypt because of the peace treaty.

"despite the stupidities of the Arab rejectionist states and their childish screams," he said, "despite the filth and the curses, I tell them, never forget that Egypt brought you from defeat to victory." He said he was putting the treaty to a referendum "because it determines the future of all coming generations" and "so that the Arab leaders who are barking today listen to the word of the Egyptian people."

Egyptian officials have been stung and upset by the near-unanimous condemnation of the treaty by other Arab states, even some that formerly were considered supporters of Egypt, and by the surprisingly vocal, although very limited, opposition here at home. Armed with the endorsement of the voters, Sadat will be able to push ahead to the next step, return of the northern Sinai coast and the key town of El Arish to Egyptian control next month-a step that will support his argument that his is the correct approach to the Israelis.

Sadat spoke calmly, simply, almost paternally tonight in his first direct address to Egyptians since the signing of the treaty last month.

Most of his 90-minute address was taken up with the domestic changes and constitutional amendments he wants approved in next Thursday balloting. He called on Egyptians to approve the dissolution of the parliament, new elections, and changes in the laws governing poltical parties, the press and foreign policy.

Assuming that the proposals are approved, the People's Assembly, whose members were elected in 1976 for five-year terms, will be dissolved immediately. The constitution then requires that new elections be held within 60 days. Sadat said he was doing this not because the existing parliament had acted badly but because it was time to reshape the state for the new circumstances it now faces.

Although Sadat's own National Democratic Party is considered certain to command as hefty a majority in the new parliament as it does in the present one, there are likely to be lievly contests for many seats from opposition and independent candidates-a party in the Arab world. Sadat noted as much with another gibe at the other Arabs, saying "I want the Arab countries where people live under terrorism and murder to see what the Egyptian citizen is doing."

Throughout his more than eight years in office, Sadat has sought to dismantle the police state, single-party repressive system he inherited from his predecessor, Gamal Abdel Nasser, while putting limits on how far freedom and democracy will be permitted to go. All Egyptian institutions, although freer than their counterparts in other Arab countries, operate under undefined guidelines based on Sadat's view of the "Egyptian Family" and national morality and responsibility.

Sadat proposed tonight that the constitution be amended to permit "freedom of formation of political parties." But he also made clear that this freedom will be limited by his sense of how far it should go.

Parties based on "corruption and feudalism" would not be permitted, he said-a blow to the hopes of the long-suppressed Wafd, the dominant political organization in Egypt before the 1952 revolution, which tried a comeback last year and was blocked by Sadat before it got off the ground. Without naming the Wafd, Sadat scorned it as representing "the peak of opportunist politics" and said it would not be tolerated. In addition, the Communist Party is illegal and Sadat has long banned any party based on religion.