After a 14-year decline, the average score on reading and vocabulary in the nation's largest college entrance exam stabilized this year, while the average score on mathematics continued to fall.

The College Entrance Examination Board reported yesterday that the average verbal score of the approximately 1 million college-bound high school seniors who took its Scholastic Aptitude Test (SAT) was 429 last spring, the same as the year before.

In the math section of the test, the average score dropped two points, from 470 to 468.

The board also reported that average high school grades given students taking its tests declined for the second consecutive year, indicating that the wave of grade inflation that engulfed the nation's high schools since the late-1960s may now be receding.

"Sometimes we see wobbles in test scores from year to year so it's impossible to know whether these are really major changes in the trends," said Robert G. Cameron, director of the college board's admissions testing program. "But there is considerable evidence among school people that they've been able to make some moves to tighten standards. We may be seeing the effects of that."

From 1963 to 1977, the average score on the verbal section of the SAT, whose multiple-choice questions test reading comprehension and vocabulary, dropped 49 points from 478 to 429. Mathematics scores declined 32 points, from 502 to 470. The highest score on each test is 800.

Last year a study panel headed by former secretary of labor Willard Wirtz concluded that the score declines signaled a substantial drop in academic achievement caused by a variety of factors, including lower standards in schools and the impact of television.

The increased number of blacks and woman taking the tests also caused part of the drop, the panel said. But it stressed that there were far fewer students scoring in the upper ranges of the SAT as well as many more scoring in the lower ranges.

The 1978 score report shows a continued increase in the number of women taking the test - now 51.6 percent of the total, and of blacks, now 9 percent.

On average, women scored 8 points lower than men in reading and vocabulary and 50 points below in maths. Last year the gap widened slightly in reading, the board reported, and narrowed slightly in math.

No information is given on test scores this year by race. However, the study panel reported last year that overall blacks averaged about 100 points below whites on the SAT.

In addition to its Scholastic Aptitude Tests the college board also administers exams to college-bound high school students in writing and in 15 academic subjects. Most of these continued to decline slightly, the board reported, although there were increases in three languages - Russian, Spanish, and Hebrew.

Yesterday, Cameron said the leveling off of SAT verbal scores may reflect efforts to raise high school standards as well as the arrival of "a more traditional group, than you had several years ago."

He said the continuing decline in math scores was "a big puzzlement," particularly because surveys indicate that high school students now are taking more math courses now than they did in the early 1970s.

Alexandrer W. Astin, director of an annual nationwide survey of college freshmen, said he was "happy" that verbal scores are no longer falling, but he added, "It's still fairly depressing to see how low they are. The decline really was tremendous and none of it has been made up yet."

Astin, who is a professor at the University of California, Los Angeles, said the continued decline in the SAT math scores was "sad."