The House, signaling strong bipartisan dissatisfaction with Reagan administration policy in South Africa, voted overwhelmingly yesterday to impose tough new sanctions in an attempt to force an end to the system of racial discrimination there.

The 295-to-127 vote came after the Democratic-controlled House rejected by similar margins two GOP efforts to delay implementation of sanctions and a proposal by Rep. Ronald V. Dellums (D-Calif.) to make them much more extreme.

Nearly one-third of Republicans -- 56 members -- joined 239 Democrats in approving sanctions. Voting against were 121 Republicans and six Democrats.

On Tuesday, the Republican-controlled Senate Foreign Relations Committee unexpectedly adopted legislation similar to, though not as far-reaching as, that approved by the House yesterday.

Sponsors of the House measure said the vote was a clear signal that the administration must stiffen its stance toward South Africa's apartheid system of segregation.

"This clearly demonstrates that the House of Representatives is for a change in policy . . . , " said Rep. William H. Gray III (D-Pa.), one of the bill's chief sponsors. He said South Africa should now realize that it must change its ways or Congress may take "even stronger measures."

The House measure would ban new loans to and investment in South Africa, stop the sale of computers and computer parts to the government and halt importation of krugerrands, the South African gold coins.

U.S. banks last year had $343 million in outstanding loans to the South African government and $4.6 billion to the private sector, according to the House Democratic Study Group. Last year, Americans bought about $600 million worth of krugerrands, more than half of the number exported.

The measure imposes stiff penalties for violating sanctions, ranging from a $50,000 fine and five years in jail for individuals to $1 million fines for organizations or businesses.

The bill would permit President Reagan to waive for a year bans on new investment and importing of the gold coins if he determines, and Congress agrees, that South Africa has met one of eight conditions in the bill. For each additional condition met, the waiver could be extended for six months.

The conditions would require South Africa to eliminate policies prohibiting black employes and their families from living together near their place of employment, eliminate "influx control" policies that restrict blacks from seeking employment where they choose and end policies that give black and white South Africans different rights of citizenship.

South Africa would also have to stop removing blacks from certain locations because of race or ethnic origin, eliminate residence restrictions based on race and ethnic origins, begin talks with black leaders on a nondiscriminatory political system, reach an internationally recognized agreement on Namibia and free all political prisoners.

During debate, supporters of the bill said the administration policy of "constructive engagement" -- working behind-the-scenes to produce change -- has resulted in nothing significant.

They called the bill's economic sanctions "moderate" but a proper response to escalating racial violence in South Africa. They also said that, in the eyes of South Africa's 22 million blacks, "constructive engagement" has put the United States on the side of a repressive white-minority government.

Rep. Howard E. Wolpe (D-Mich.), one of the bill's sponsors, said supporters have the "profound belief that this is the only way" to make South Africa change and "avert some of that bloodshed we see down the road. There is a bipartisan consensus that 'constructive engagement' has had enormously destructive consequences."

Opponents said sanctions would increase tension just as South Africa is indicating willingness to change. They said sanctions could lead to increased violence, eliminate many jobs for blacks and reduce U.S. influence in the region.

Many of the 56 Republicans who voted for the sanctions are liberals or moderates. They were joined by a few conservatives, including several who signed a letter in December to the South African ambassador demanding greater change.