Yosef H. Yerushalmi, chairman of the Near Eastern Languages and Civilization Department, will leave Harvard this summer for a position as director of the Columbia University Center for Israel and Jewish Studies and as the Baron Professor of Jewish History, Culture and Society.

Robert W. Thomson, professor of Armenian, has replaced Yerushalmi as department chairman, Dean Rosovsky said yesterday. Thomson held the position from 1973-78.

Rosovsky added that Yerushalmi is "one of the finest" in his field, and his departure will be a great loss.

"I am not leaving Harvard without regrets," Yerushalmi said yesterday, adding "I have many ties here, many friends, but you can be very happy and still want to move."

Yerushalmi came to Harvard in 1966, after receiving his doctorate from Columbia, studying under Salo W. Baron. Four years later he received tenure at Harvard as he became Safra Professor of Jewish History and Sephardic Civilization in 1979.

The attractions of Yerushalmi's native New York City helped lure him from Harvard. "I want to be a city man again," he said last night. He added that he leaves also for a sentimental reason: to occupy the chair honoring his former teacher.

Yerushalmi anticipates close cooperation between the Columbia Center and Harvard's Center (opened last October), including jointly sponsored colloquia, international conferences, and perhaps exchange programs for graduate students.

He is attracted by the challenge that the Columbia position presents, especially allows him to "expand and build" the Center.

J.M.W. Bean, chairman of the history department at Columbia regards Yerushalmi's appointment as "an enormous asset and a tremendous addition to our resources." The center's present director, Marvin I. Herzog, added that individual," and his appointment is widely acclaimed at the university.

Richard N. Frye, Aga Khan Professor of Iranian said the department is "sorry to see him go," adding that it will be difficult to find a replacement of his quality.