WASHINGTON (AP) _ President Reagan praised a child care proposal by Vice President George Bush, calling it a means of allowing women to choose to stay home with their children if they want.

Reagan told a group of evangelical young people Thursday the plan would ''strengthen the family'' because ''the basic idea here is that the government would simply let families keep up to $1,000 more of their own money.''

''That's money the family itself can decide how to spend,'' Reagan said. ''Working mothers could put the money toward child care. But by giving each family this tax credit the vice president's plan would also permit thousands of mothers to choose to stay home with their children.''

It was Reagan's first comment on the proposal, which Bush is making part of his own presidential campaign.

In the speech to the Student Congress on Evangelism at the Washington Convention Center, Reagan also reiterated his opposition to abortion, saying, ''We cannot proclaim the noble ideal that human life is sacred, then turn our backs on the taking of some 4,000 unborn children's lives every day.

''This must stop,'' the president said. ''An abortion is the taking of a human life.

''Many who seek abortions do so in harrowing circumstances,'' he added. ''And just as tolerance means accepting that many in good faith hold views different from our own, it also means that no man or woman should sit in judgment on another.

''I believe - and Vice President Bush believes with me - that we must rise above bitterness and reproach to find positive answers to the tragedy of abortion.''

Reagan said his administration has sought to reflect a ''return to basic values'' through such steps as the enactment by Congress of the Equal Access Act of 1984, giving voluntary religious groups the right to meet after school on the same basis as other groups. He also cited longstanding administration positions in support of returning prayer to the classroom and reversing the Supreme Court decision that legalized abortions.

He said legislation his administration has submitted to deal with child pornography is being held up in Congress, and asked, ''If the House and Senate leadership really care about family values, isn't it time they brought this anti-pornography legislation to a vote?''

He also talked to the young men and women about the pressures teen-agers feel to have sex out of wedlock.

''I'm sure that each of you believes that someday you'll find someone to fall in love with - and you will,'' he said. ''You know that when you meet that person, and meet in a marriage, that you will be true to each other. Well, did you ever stop to think you can start being true to that one special person beginning now?''

The 8,000 young people cheered wildly, applauded, stamped their feet and jumped up and down as the president made his appearance in the cavernous hall.

He opened by leading the group in the pledge of allegiance to the American flag, and ended by joining others in the crowd in waving a small flashlight in an effort to keep time to the music as the group sang a song proclaiming, ''We will carry the torch of the Lord.''