WASHINGTON (AP) _ Reeling from a record year of natural disasters, the American Red Cross staged ''Un-Disaster'' Day on Wednesday, a nationwide series of money-raising events aimed at refilling the charity's depleted coffers.

''Americans must act now on behalf of the American Red Cross, so it can act on their behalf in the future,'' Sen. Jeremiah A. Denton Jr., R-Ala., told a Washington gathering.

And entertainment stars took the podium in Los Angeles to urge support for the charity.

The two events brought together politicians, entertainers, volunteers and media as the focus of more than 350 other local Red Cross gatherings in 46 states designed to draw attention to the volunteer efforts and financial need of the agency.

The event also premiered the new song, ''I'll Pull You Through,'' a ballad extolling the Red Cross sung by Mark Campbell and Cynthia Fee.

Performed at noon Eastern time, the song also was played by a national hookup at other Red Cross events. Radio stations nationwide had been furnished copies and asked to participate by also playing it at noon.

In a normal year the Red Cross assists Americans at an average of 110 disasters a day, ranging from widespread hurricanes and floods to the most common of disasters - apartment and house fires.

But 1985 was not a typical year, said Red Cross President Richard F. Schubert.

Officials said the Red Cross has launched a fund-raising campaign because it expected a $26 million deficit to be accumulated by the end if its fiscal year in June - due largely to disasters in the last half of 1985.

''I can announce today that thus far, the Red Cross emergency campaign has received $9 million. We still have much more to accomplish, of course, but I believe that Americans will respond to their Red Cross in this hour of need for the victims of disasters,'' Schubert said.

The most hurricanes to strike the nation since 1916, combined with floods and mudslides in Puerto Rico and flooding in Virginia and West Virginia helped use up $37 million in disaster assistance so far - already more than the planned disaster budget for the year with six months yet to go.

And Schubert noted that the spring flooding season remains ahead, as well as the Red Cross normal preparedness activities.

Other events across the country included:

-A Red Cross truck was to be carried by barge from Oakland to San Francisco and taken ashore by crane, to symbolize the kind effort likely to be needed in the event of another earthquake.

-Campaign lunches were scheduled in Detroit and Pontiac, Mich., with presentation of a $418,000 check planned.

-In Pittsburgh, the public was invited to a downtown YMCA to talk to a local meteorologist, get blood pressure checkups and see first aid demonstrations.

-First aid demonstrations were also scheduled in Seattle, with elementary school youngsters playing earthquake victims and teen-agers administering first aid.

-Special honors were to be presented to 17 local volunteer workers in Philadelphia, along with recognition for other agencies which help in disasters including police, fire departments and the city's emergency office.

-In Boston, a bank lobby was converted into a disaster center, with first aid stations, ham radio operators and other assistance stations.

-Volunteers who helped during floods in November were to be honored at two shelters in downtown St. Louis.