NAACP members convening here voted unanimously today to boycott U.S. films and movie studios that do not give blacks reasonable access to jobs in front of and behind cameras.

Before the vote, a panel of blacks from the movie industry told the delegates that of the 240 movies released by major studios last year, a black actress played in only one major role and black actors had only 12 significant parts. When blacks do get work, they said, the roles tend to be stereotyped and demeaning.

"The motion picture industry is about 20 years behind other industries in this country in terms of integration," said Geraldine Greene, president of the Hollywood-Beverly Hills chapter of the NAACP.

An NAACP study committee that has been working on the issue since early this year found that blacks make up about 30 percent of the theater-going public in the United States and contribute about $400 million each year to the industry.

Curtis Rodgers, acting chairman of the committee studying the film industry, said the NAACP has three possible weapons against studios that refuse to cooperate: lawsuits, administrative complaints to the federal government or what he called a "selective patronage campaign."

Rodgers said the final alternative would involve not only boycotts of targeted films by the 450,000 NAACP members in 1,800 chapters nationwide, but also picket lines outside theaters in key market areas where others would be urged not to attend the film.

He said the first step would probably be to target one or two films or studios.

The concept of economic boycotts against companies or industries that discriminate against blacks in employment or promotion has been a major theme of the convention.

As Benjamin L. Hooks, executive director of the NAACP, told delegates, "Mr. Reagan has told us to vote with our feet. Well, we're going to vote with our feet by not utilizing those industries that have refused to treat us with respect and dignity.

"I am not going to spend another dime as long as I live anywhere that folks don't respect me," he said. "We're insisting that every company in this country have some blacks on its board of directors."

Lynn Moody, who played a major role in the television mini-series "Roots," said she has had only two small roles this year, and "I'm told I'm one of the lucky ones. Last year there was one opening in a leading or supporting role for a black actress, and there were none the year before that."

Georg Stanford Brown, who played Moody's husband in "Roots" and is also director of the "Cagney and Lacey" television series, said, "I have not worked for over a year as an actor--not by choice."

Rodgers said the NAACP has met with representatives of most of the major film studios over the past six months. He said industry representatives have generally been "intractable but genial."

The NAACP will probably not be ready for a specific boycott until September, Rodgers said, but the delegates voted unanimously to authorize the leadership to go ahead with planning.

Bernie Casey, an actor and former professional football player, said, "We don't know how strong we are. As we confront Reaganomics and the insanity that comes out of the White House. . . . We can't just sit around and do nothing. If we do nothing, nothing will be done.

"They have dealt to us the ultimate insult. Because of inappropriate black roles they have said you do not even exist. . . . We pay our hard-earned dollars to support the statement that we do not exist."