Soviet officials Monday capped the biggest shake-up in Mikhail S. Gorbachev's 31/2 years in power by replacing Politburo member Vitaly I. Vorotnikov as premier of the Russian republic.

The Supreme Soviet of the Russian Republic, the largest of the 15 Soviet republics, elected Interior Minister Alexander V. Vlasov - an ally of Soviet leader Mikhail Gorbachev - as the new premier. Vlasov was named a candidate member of the Politburo during a central committee meeting Friday.The 62-year-old Vorotnikov was moved to the ceremonial job of president of Russia. Vladimir P. Orlov, the 67-year-old president of the republic, retired.

Vlasov had been named a candidate member of the Politburo during a Central Committee meeting on Friday.

Tass, the Soviet news agency, said Gorbachev recommended the changes.

The latest changes come after Gorbachev led the most dramatic political changes in the Soviet leadership of his 31/2 years in power.

Monday's meeting of the Russian Supreme Soviet in the Grand Kremlin Palace comes two days after the national parliament elected Gorbachev the country's president to replace 79-year-old Andrei A. Gromyko.

On Friday, Gorbachev pushed a major shake-up through the Communist Party's policy-making Central Committee. He retired two full and two candidate Politburo members, promoted four other people and streamlined the Central Committee's apparatus.

Vorotnikov and Ukrainian Communist Party leader Vladimir V. Shcherbitsky are the only two members of the ruling 12-man party Politburo who were there before Gorbachev took power.

One Western diplomat in Moscow, who spoke on condition of anonymity, said Vorotnikov was considered a "swing" vote on the Politburo. He generally supported Gorbachev's reforms, but was "not real outspoken, cautious, not zealous," the diplomat said.

Vlasov had worked in Gorbachev's home area of southern Russia before becoming interior minister, in charge of the police, in 1986. His replacement is to be named by national authorities.

Vorotnikov was first deputy premier of the Russian republic in 1975-1979, but lost the support of the Kremlin leadership in the last years of President Leonid I. Brezhnev and was made ambassador to Cuba. He was summoned back to Moscow after Brezhnev's death in 1982, and became premier of the republic the following year.

Gorbachev's election Saturday by the 1,500 deputies of the national Supreme Soviet unified the party and gave him both the top government and party jobs - and more power to force through his programs of reform.