John Fisher Zeidman, 20, until recently a student at Peking Normal University in Peking, China, and a lifelong resident of Washington, died Sunday at Johns Hopkins Hospital in Baltimore. He had viral encephalitis.

Mr. Zeidman was a 1979 graduate of Sidwell Friends School. He studied at Boston University and later completed two years at Duke University in Durham, N.C., where he was a member of the Campus Council and the Council on Residential Life.

Last summer, he went to China for a year of study and travel administered by the University of Massachusetts. He had completed a course at the Institute for National Minorities in Peking and was a student at Peking Normal University when he became ill in September. He was hospitalized in Peking until Oct. 22, when he returned to this country.

Mr. Zeidman had been an intern at public television stations in Washington and Boston. During the 1980 presidential campaign, he was a press aide with the Carter-Mondale Reelection Committee in Washington.

Survivors include his parents, Mr. and Mrs. Philip F. Zeidman of Washington; two sisters, Betsy of New York City, and Jennifer of Washington, and by two grandparents, Mr. and Mrs. E. M. Zeidman of Birmingham, Ala.