A White House demonstration yesterday marking the finale of a five-week "Harvest of Shame" protest against Reagan administration policies on nuclear arms, Central America and the homeless resulted in 74 arrests, law enforcement officials said.

About 200 singing, chanting demonstrators crowded the sidewalk in front of the mansion from 11 a.m. to 1 p.m., shouting "Reagan Dumped" and "Out the Door in '84." District police arrested 19 of about 40 protesters who sat or stood in Pennsylvania Avenue, closing the street to traffic between 15th and 17th streets for an hour.

Uniformed Secret Service officers arrested another 13 protesters who joined a White House tour line and then knelt in prayer on the grass along the driveway leading to the northeast exit from the grounds.

U.S. Park Police took 42 demonstrators into custody after they stood with banners and signs near the center of the White House fence on Pennsylvania Avenue. Interior Department regulations ban stationary signs from a 60-foot-wide "center zone" of the fence.

All of the arrested demonstrators were taken in police vans to a building at Fifth and D streets NW for processing on charges of disorderly conduct, unlawful entry or violating the "center zone" prohibition.

Those who posted $50 collateral were freed, officials said. Others were to be held at D.C. Jail for appearances Monday in D.C. Superior Court.

The Community for Creative Non-Violence, a group advocating government-financed shelter for the District's poor and homeless, launched its protest on Oct. 1, vowing to carry out daily acts of civil disobedience to call attention to the group's views.

Yesterday's arrests brought the five-week total to 228.

The demonstrators were angered last month when police declined to make any arrests on the first day of the protest. Authorities were more accommodating yesterday, escorting protesters to the waiting vans and carrying those who refused to walk.

Cries of "Take Ronnie, too" filled the air when the arrests began in the sidewalk's "center zone."

Carol Fennelly, a CCNV leader, said the group has achieved "real movement in the basic education of the American people" about the plight of the homeless through its demonstrations. "We believe there is good in everybody and that once they're educated, people will react."

The group supports Initiative 17, a measure on Tuesday's ballot that would require the District to provide shelter for the homeless.

The protesters sang "We Shall Not Be Moved" as they stood in the middle of Pennsylvania Avenue, blocking traffic. "The last time I sang this," said one demonstrator as she held a banner aloft, "I got moved."