Nine protesters were arrested outside the Soviet Embassy yesterday as part of the escalating effort by the Washington Board of Rabbis to focus attention on the plight of Soviet Jews while the two superpowers approach summit talks next month.

More than 90 persons have been arrested in six separate demonstrations since May 1, when 24 rabbis, wrapped in their long-fringed prayer shawls and carrying sacred Torahs, launched the protests.

"We want to remind President Reagan of his promise in March" to include treatment of Jews in the Soviet Union on the agenda of the summit talks, said Rabbi Ira Korinow of Haverhill, Mass., one of the nine arrested yesterday.

"Human rights in general and Jewish immigration in particular must be on the agenda," said Korinow, who answered reporters' questions before crossing 16th Street to be arrested for demonstrating within 500 feet of an embassy. Korinow was one of seven American rabbis who met with Reagan in March to discuss Soviet Jews.

The mounting protests are reminiscent of the daily weekday protests outside the South African Embassy by apartheid protesters, but Rabbi Gary Fink of the Jewish Congregation of Laurel, who serves on the Soviet Jewry committee of the Washington Board of Rabbis, said, "This is not new for us. We have simply reinstituted the style of demonstrations that we used during the '60s."

During the '70s, when the situation for Soviet Jews had improved somewhat, Jews here "hesitated to use these tactics because of the fear of the backlash" in Russia, he said. But by now, "things have gotten so bad we don't think we can make them worse."

Jewish leaders throughout the Western world have watched the deteriorating situation for Soviet Jews with growing apprehension.

Migration of Jews from the Soviet Union, a key index of Soviet treatment of their Jewish minority, has dropped from 51,320 in 1979 to 896 last year. Korinow, who visited the Soviet Union earlier this year, said that as many as 350,000 Jews have applied for permission to leave.

Many more want to leave, he said, "but they are afraid to apply" because of the harsh measures often taken against such persons. Of particular concern to Jews in the West has been the arrest by the Soviets and conviction, on allegedly false charges, of Jews who teach Hebrew, the language of the Jewish religion.

Jewish leaders here are recruiting Hebrew teachers in this country to volunteer for arrest at the next protest scheduled for Nov. 17, just before the summit talks begin. Demonstrations and arrests will also take place in San Francisco, New York and Chicago, said Rabbi I. David Oler of the Gaithersburg Hebrew Congregation.

Last week, 22 college students were arrested at the embassy here. Last month, on the Jewish holy day Yom Kippur, four Christian leaders were arrested.

Unlike the thousands who have been arrested and then released in the South African demonstrations, persons arrested for demonstrating at the Soviet Embassy are being prosecuted.

Oler, who was arrested in the first protest on May 1, said the group has moved for a dismissal of the charges on the grounds of "selective prosecution." A decision is pending.

"If that's rejected, our defense will be religious necessity," he said, "the Biblical injunction not to stand idly by while our brothers' blood is being shed."

The U.S. attorney's office has said the decision to prosecute is made on a case-by-case basis and that the arrests at the South African Embassy lack prosecutive merit.