The number of white students in Prince George's County schools dropped this fall by 10.4 percent, the steepest decline yet in six years of heavy enrollment losses that have followed the start of court-ordered busing.

Blacks now account for 44 percent of the students in Prince George's schools, according to a new official enrollment report, compared to 25 percent just before busing for desegregation purposes began in 1973. Last fall blacks made up 40.7 percent of Prince George's school enrollment.

"If the trends keep going the way they are, the system can soon become 50 percent black,' said school board president Norman Saunders. "It could even become 70 percent black. There are a good many parts of the county that are resegregating themselves."

Even though the 1973 court desegegation order that sought to make each county school between 10 percent and 50 percent black, the massive loss of whites and the continued increase of blacks has drastically altered the racial balance.

This year 94 of Prince George's 226 schools have black majorities, including 10 that are more than 80 percent black.

On the other hand, six elementary schools are now less than 10 percent black.

Nearly all of the heavily black schools are between the District of Columbia line and the Capital Beltway where the black population has risen rapidly in recent years. The county's few almost all-white schools are near Laurel and Bowie, where new construction has taken place.

Although the federal desegregation case was concluded in 1974, the school board has made almost no changes in attendance boundaries since the busing order went into effect in 1973. Last year a plan to reduce busing in areas that become integrated in the past five years was shelved after widespread criticism.

Board members said they were fearful that any boundary changes might prompt a new lawsuit by the NAACP, which brought the original desegregation case.

Enrollment in Prince George's schools has been declining overall, and Saunders said the board now intends to decide which schools to close with the help of citizens committees. Then, he said it will try to reduce busing, probably by September 1980.

According to the new report, enrollment in Prince George's schools declined this fall to 133,613-5,689 less than a year ago. The loss of 8,167 whites was offset partly by a gain of 2,074 blacks and 404 youngsters of other races, mostly Asian and Hispanic.

The black increase this year, however, was almost 1,000 less than last year, and the smallest since 1966. Charles Wendorf, the director of pupil accounting said transfers from the District of Columbia, which has provided most of Prince George's new black students, dropped by about 800 compared to last year.

Wendorf suggested that many blacks leaving Washington may be moving to suburbs other than Prince George's.

The loss of whites, Wendorf said, has occurred partly because of a drop in births and because few white children are moving into the county to replace those who graduate or move away-a situation that has prevailed since busing started.

Overall, the number of white children attending Prince George's schools has dropped by 48,724 since 1972, a decline of 41 percent, while the number of black children has climbed by 18,388 or 45.5 percent.

In 1973, the first year after busing, the school system lost the most white students over, 11,224. But the rate of decline is greater now-10.4 percent, compared to 9.4 percent-because fewer whites are left.

Although white members of the school board appear concerned about the loss of white students, Bonnie Johns, the only black on the board, said yesterday:

"I cannot spend my time begging, pleading and enjoining people to come back into the school system. I am determined to make this the best possible school system for the children who are here now. They're the ones I'm committed to. . ."