Benjamin Levich, the highest-ranking Soviet physicist ever to apply to emigrate, yesterday was told he has permission to leave the Soviet Union, thus apparently ending a six year and eight months struggle highlighted by the personal intercession last month of Sen. Edward M. Kennedy (D-Mass.) to Soviet President Leonid Brehzhnev.

Levich, 61, whose work in the field of hydrodynamics has brought him world renown, said yesterday, "I was assured by Academy of Science officials that I have permission to emigrate and this was confirmed by Interior Ministry officials."

The scientist, a corresponding member of the prestigious academy, and his wife, Tanya, first applied to emi-Union's most prominent "refused-by authorities on the glround of state secrecy, and became one of the Soviet Union's most prominent "refused niks," Jews refused permission to emigrate.

His case was taken up by Kennedy during a two-hour conversation the senator had last month with Brezhnev in the Kremlin while Kennedy was visiting here.Kennedy also mentioned 17 other families he was concerned about who were also attempting to leave.

Kennedy announced in Washington after his return that he expected the Soviets would act soon on all the requests and allow the people to leave, some for the U.S., some for Israel. His announcement was attacked by Pravda, the Communist Party newspaper, on grounds that he was trying to interfere in the internal policies of the Soviet government.

A number of those on the "Kennedy list" were disheartened, although a Kennedy aide said at the time he expected that the Soviets would give them permission. It was reported last week that several of those on the list were not long-time refusedniks, as Kennedy had characterized them, but people who had already received permission to visit the U.S. as a tourist.

The leviches said they intend to live in Israel. Levich has received requests from more than two dozen U.S. universities to take a teaching position, including Massachusetts Institute of Technology and the Case Western Reserve Institute in Cleveland. The couple's two sons, both scientists, were allowed to emigrate three years ago. In 1974, the Leviches were told by police authorities they would be allowed to leave if they promised not to try to make contact with members of President Nixon's party who were here on an official visit. The Leviches agreed, but the authorities subsequently allowed only the sons to leave.

Since then, Levich's cause had been taken up by physicists in many Western countries. Last year, a special symposium held at Oxford University, England, in Levich's honor resulted in more than 40 scientists sending a telegram pleading his case to Brezhnev. In addition, at least five other members of the Soviet Academy of Sciences sent their congratulations to the Oxford meeting, a rare gesture for people whose highly privileged life styles depend to a considerable degree on avoiding politics.

Levich's speciality is electrochemical kinetics, the study of the chemical and electrical properties of substances in motion. His internationally acclaimed work in this field was abruptly terminated when he sought an exit visa. He was fired from his professorship at Moscow State University and removed from his post as department head. His special research chair there was also eliminated. Levich's name was removed from his published scientific papers and books, and he was dismissed from various advisory groups.

Last year he was attacked by Literary Gazette as an incompetent plagiarist who had defamed his homeland.

Levich is officially now called a "researcher." He said he will resign from his phantom post, as required of those who receive permission to emigrate. He and his wife say they will complete the required paperwork for the application and hope to leave within a few weeks.

Early next month, a second symposium honoring Levich is scheduled. It will be held Nov. 6-8 in Washington at the National Academy of Sciences, and Levich would like to be there.