The Senate passed President Nixon's draft-lottery bill yesterday, and sent it to the White House.

The new law-needing only Nixon's signature to take effect-will substitute a single years of draft eligibility for the seven years of uncertainty that draft eligible men now face.

The lottery system, based on a random selection of birth-dates, will draw men from a pool of 19-year-olds, instead of following the present policy of drafting the oldest men first.

Secretary of Defense Melvin R. Laird said the Selective Service will try to implement the lottery in time to pick the next group of draftees in January.

Men who would be draftable under the present system will not escape the draft just because they passed the age of 19 before the new system takes effect. These men will be placed in the lottery as if they were 19 years old.

Nineteen-year-old students will continue to receive educational deferments, but they will be placed in the pool when their deferments run out.

The lottery will work by scrambling the days of the year. and then drawing them at random, each date being assigned a consecutive number.

"If number one is November 15, all those born on November 15 would be in the highest priority for call," said Senator John Stennis (D-Miss). chairman of the Armed Services Committee. "If November 20 were to receive number 365, all those born on this day would be in the lowest order for call." he explained.