The University of Maryland yesterday took a significant step toward tightening admission standards for incoming freshmen.

The new policy, recommended by the Board of Regents' education policy committee and due for a vote by the full board next month, would reduce the number of students guaranteed a place in the freshman class by raising the college board scores and grade point averages now used as requirements for guaranteed admission.

Chancellor Robert L. Gluckstern said yesterday that between 200 and 500 students would have been rejected this year if the new admissions criteria had been used to screen the class of some 4,500 freshmen who arrived at the College Park campus this fall.

The university is already operating under state guidelines requiring it to reduce the size of its freshmen class by 100 students each year until it reaches a class of 4,000.

The new policy is expected to win approval from the full board and to go into effect in the fall of 1983.

It is the latest in a series of steps taken by the University of Maryland administration and the Board of Regents to enhance the school's image as a serious academic center that can attract the state's top high school students.

"This is partly an effort made by the university to upgrade itself in the eyes of its constituents in the state," Gluckstern said. "The university has been viewed by some as a place that is easy to get into, and not as the fine institution that it really is."