"Before the conference begins," said the man from the State Department, "we send them all out together to shoot the rapids of the Colorado River.

"It loosens them up."

He was explaining the unusual diplomatic program that had brought together 200-plus senators, ambassadors, development bankers, corporate executives and ordinary American citizens in the State Department's enormous, marble-walled Benjamin Franklin Room to eat roast beef and stuffed tomatoes, hear a talk by Ambassador Robert Strauss and witness the presentation of a ceramic bald eagle to former Secretary of the Treasury Robert B. Anderson.

In the bipartisan spirit that is always sought in foreign policy, Sens. Charles Percy (R-Ill.) and John Sparkman (D-Ala.) jointly gave the award to Anderson.

It was a program originated by Anderson in the early '60s that will send 17 foreign diplomats and economic experts on a wilderness trek with nine American business executives before they settle down next week for a two-day conference in a lodge on the brink of the Grand Canyon. The theory is that four days in the wild will put international economic problems in a new perspective and shake the conference participants out of their usual roles.

Anderson also originated another idea represented at the State Department luncheon - sending foreign diplomats to live for a few days with an American family, so that, as he said yesterday, "those who come to represent their countries in our country should not bring back home an image of America that is generated either in Washington or in New York."

More than 1,000 foreign diplomats have stayed with American families under this program, and according to some of the hosts who were at the luncheon yesterday, it has changed their impressions of America.

"Our guest had never really known a black American family before," said Mrs. Frank Monteith of Atlanta, whose husband operates the limousine service from the Atlanta airport. "He ate with us, went out to shows with us, watched the 11 o'clock news on television and helped us cope with the children. I think a few of his ideas were changed."

Another hostess, Mrs. Karl Victor of Louisville, arranged the group activities for 21 diplomats during their four-day stay with Louisville families and recalled that their first visit was to a local distillery - a loosening-up resource comparable, perhaps, to the Colorado River rapids.

The tour included various industries, Churchill Downs, the birthplace of Abraham Lincoln and othe points of interest, she said, "but their greastest thrill was meeting Colonel Sanders in person."