Soviet Communist Party leader Leonid Brezhev was named president of the Soviet Union, the country's ceremonial chief of state, today in a symbolic move that caps more than a decade of Brezhev's steadily growing power in the Kremlin.

Brezhnev replaces Nikolai Podgorny, who was ousted from the ruling Politburo last month apparently because he refused to give up the presidency to the party chief.

This morning, at the start of the semiannual session of the national parliament, the Supreme Soviet, it was announced that Podgorny had "requested" to be relieved of the president's post "in connection with his retirement."

After a brief, ritualistic nominating speech by Mikhail Suslov, the party's long-time top ideologist, Brezhev was acclaimed and stood with his hands clasped in front of him while delegates cheered and stamped their feet.

"Discharge of the lofty and responsible state functions connected with [the presidency], parallel with the duties of the general secretary of our party's Central Committee, is not an easy matter," Brezhnev declared. "But the will of the Soviet people, the interests of our socialist homeland have always been for me the supreme law."

In terms of how the Soviet Union is to be governed, today's change will have no visible effect. As head of the Communist Party, Brezhnev was already undoubtedly the country's most important man.

But Brezhev clearly believes that as president he attains a stature in the international arena that he did not have before. For the first time he will be on a protocol par with his Western counterparts such as President Carter and French President Valery Giscard d'Estaing, whom the Soviet leader will be meeting in Paris next week..

The move is also an investiture, the elevation of Brezhev to a position from which he can preside over the country even as younger and more vigorous people soon take on some of his administrative and executive chores.

Brezhnev served as Soivet president once before, from 1960 to 1963. Ironically, his selection for the post was considered at that time something of a demotion. He had been regarded as a possible heir to Nikita Krushchev and the presidency was regarded as a sinecure, out of the direct line of key policy-making.

In fact, he was fortunate to be president during those years, because when Khrushchev was ousted in 1964 Brezhnev was not as closely identified with the fallen leader as he bad been in the past. Brezhnev was made party first secretary - later changed to general secretary - and began his rise to the pinnacle of Soviet power that today's action signifies.

Along the way, in 1970-1971, there was rumors that Brezhnev was interested in a top state job - it was thought then that he wanted Premier Alexi Kosygin's position - but the move evidently blocked. The Politburo was resisting, analyst said, a return to the Stalin - Krushchev eras when too much authority was invested in one man. The Kremlin leadership was essentially collective, with Brezhnev as first among equals.

Now Brezhnev stands alone. He is still, of course, subject to the unpredictable, to outsiders, unfathomable pressures that as Podgorny's downfall showed can mean instant oblivion. But Brezhnev had overcome every political obstacle that Western analyst said were being placed before him by Politburo rivals.

Last spring he became marshal of the Red army, the first Communist Party boss since Joseph Stalin to be so anoited. In December further honors, titles and tributes were heaped upon him as he celebrated his 70th birthday. And earlier this month a new constitution for the country was published after a long internal ideological debate over details in which Brezhnev clearly prevailed.

One of the provisions in the new constitution is for a first vice president who undoubtedly will be the person responsible for the routine functions of the presidency - which is technically the chairmanship of the Presidium of the Supreme Soviet - such as recieving ambassadors and officiating at parliamentary-type meetings.

The prevailing view now is that Podgorny fought a last-ditch effort to keep the presidency, refused any less post and was dumped as a result. Since May 24, when his ouster from the Politburo was announced, his name has disappeared from all official documents.

Disclosure today that he had retired at his own request, which spares him at least the ignominy of being publicly fired, is probably the last time his name will be mentioned officially in his lifetime.