The administrator of a fund set up by novelist Alexander Solzhenitsyn to assist Soviet political prisoners and their families was reported today to have been arrested by the security police KGB.

Dissident sources said the administrator, Sergei Khodorovich, 42, was taken into custody Thursday in Moscow after a two-hour search of his apartment. No charges have been made public.

The fund was established in 1974 with money that the Solzhenitsyn family left behind following his expulsion from the Soviet Union. It operated partly on royalties in the West from "The Gulag Archipelago," Solzhenitsyn's extensive study of the Stalinist penal system. Initially, "The Gulag Archipelago" royalties were sent into the Soviet Union through legal transfers, with the Soviet authorities taking a third off in taxes and passing along the rest in rubles.

When the authorities learned about the fund, which was used to assist hundreds of political prisoners and their families, they blocked further payments to Alexander Ginzburg, a friend of Solzhenitsyn who originally administered the fund. Ginzburg was arrested and convicted of anti-Soviet agitation in 1977 and later was released in a prisoner exchange.

Khodorovich, a computer programmer who took over the administration of the fund in 1977, is believed to have received money from abroad through unknown Russian intermediaries. Some of the money used by the fund had been raised in the Soviet Union.

A Leningrad representative of the fund, who was arrested 16 months ago, last month appeared on Soviet television to say he had been manipulated by U.S. intelligence agents. Khodorovich was detained for 10 days last May after his apartment was searched, but he was released at that time.