Poland's military ruler, Gen. Wojciech Jaruzelski, received an effusive welcome and expressions of strong support here today for what Soviet President Leonid Brezhnev termed Poland's "national decision" to impose martial law in December.

After exchanges of hugs and kisses and a military ceremony at Vnukovo Airport, Jaruzelski was driven to the Kremlin along a route draped with Polish and Soviet flags. Thousands of people were in the streets to cheer the visitor.

During a Kremlin dinner speech, Brezhnev said the "timely decision" to put an end to a "protracted, excruciating crisis" already has raised the prospect of "better days" to come.

"Had the Communists given way to counterrevolution, had they wavered under the furious attack by the enemies of socialism, the destiny of Poland and stability in Europe and in the world at large would have been jeoparized," the Soviet leader said.

Brezhnev pledged continued economic assistance to Poland. "We helped socialist Poland the best we could and we shall continue helping it," he said.

In his reply, which largely emphasized Poland's economic difficulties and "significant complications" caused by U.S. economic sanctions, Jaruzelski pledged to build socialism in Poland "on the principles of Marxist-Leninist science" while taking into account "concrete conditions" including "Polish traditions and culture."

Jaruzelski toasted the "unbreakable friendship" and "unshakable alliance" between the two countries. Virtually all high Soviet officials present in Moscow attended the dinner.

Jaruzelski, who is on his first foreign visit since he became head of Poland's Communist Party in October, was accompanied by the chief-of-staff of the Polish Army, Gen. Florian Siwicki; Foreign Minister Jozef Czyrek; Roman Malinowski, leader of the Polish United Peasants Party, and Edward Kowalczik, leader of the Democratic Party. Also in the delegation was Politburo member Zbigniew Messner.

Soviet officials at the arrival ceremony included six members of the Politburo--Premier Nikolai Tikhonov, Defense Minister Dmitri Ustinov, KGB chief Yuri Andropov, Foreign Minister Andrei Gromyko and Konstantin Chernenko.

The airport turnout and massive publicity given to the Poles symbolized the importance attached to the visit.

The two-days of talks are expected to focus on Jaruzelski's plans to seek a political resolution of the crisis and on Poland's economic situation.

The government news agency Tass quoted Brezhnev as saying that the first day of talks was marked by "an identity of views and an identical understanding of current and future tasks." He described the atmosphere as one of "friendship, comradely solidarity and cordiality."

In his dinner speech at the Grand Kremlin Palace, Brezhnev praised the Jaruzelski government's efforts "to clear the practice of socialist construction of everything extraneous and alien to the nature of socialism." He expressed concern that the leading role of the Communist Party be restored.

Brezhnev referred to the situation in Poland as still being "complicated and sometimes dramatically difficult." This conforms with the view stated here that counterrevolution in Poland has been "checked" but that is has not been defeated and that therefore martial law should not be lifted soon.

The key question in the talks is believed to be the framework of any future discussions between Polish authorities and elements in the suspended trade union Solidarity and the Roman Catholic Church.

Although the Polish Communist Party's Central Committee met last week, there have been no clear signs as to its plans for dealing with the union and church. If there are differences of opinion between Moscow and Warsaw, they are likely to be in this area.

From his public statements, Jaruzelski seems prepared to free most of the 4,000 Solidarity members interned under martial law if the union drops its resistance and helps the government mobilize the population to revive the economy.

No differences of view were visible during today's ostentatious show of Soviet-Polish friendship, as Jaruzelski visited the graves of Felix Dzherzhinsky, the Polish-born founder of the Soviet secret police, and Konstantin Rokossovsky, the Polish-born Soviet marshal who was virtual military governor of Poland in the postwar years.

Brezhnev's speech was largely conciliatory, although he accused the United States of "increasing pressure" on Poland in an effort to bring "new trials and ordeals" there.

He said the issue of Poland should not stand in the way of East-West cooperation. "We stand for brushing aside the mounds of accusations and counteraccusations and for getting down to a practical solution of urgent problems," he said.