CALGARY, FEB. 26 -- Viktor Tikhonov, the dour head coach of the Soviet Union's hockey team, was caught smiling late in the first period of his team's game with Sweden tonight.

It was the briefest of grins, but its meaning was obvious: For the seventh time in the last nine Winter Olympics, the Soviets were going to win the gold medal.

The U.S.S.R., unbeaten in 15 consecutive Olympic games dating back to 1980, defeated the Swedes, 7-1, tonight at the Saddledome. Because Finland was upset by Czechoslovakia, 5-2, earlier in the day, the Soviets are assured of winning the gold medal no matter what happens in Sunday's final games.

As things stand now, Finland would win the silver medal and Sweden the bronze. However, Canada still has a chance to win a bronze medal if it beats Czechoslovakia Saturday and West Germany upsets Sweden Sunday. The Soviets finish with Finland Sunday.

With a three-goal barrage in 1 minute 41 seconds late in the first period, the U.S.S.R. put pesky Sweden away and won for the 30th time in 31 Olympic hockey games, dating to the 1968 Olympics in Grenoble, France. The only loss was the United States' 4-3 victory at Lake Placid.

When it was over, the Soviets showed an uncharacteristic burst of emotion, hugging goaltender Sergei Mylnikov and throwing their sticks into the stands.

For them, the gold medal was a vindication of sorts after a difficult year in which they lost the world championships, the Canada Cup and their own Izvestia tournament.

"There has been a lot of criticism of the team and the coach," Tikhonov said tonight. "I think the Olympic Games will change the opinion of many about the strength of the Soviet national team."

The Soviets were determined not to lose tonight, not against a Swedish team that had little offensive punch due to the absence of world championship stars Bengt Gustafsson, Hakan Loob and Tomas Sandstrom, all now back in the NHL. Sweden won the world title with them. It couldn't come close to the Soviets without them.

Sweden managed only 13 shots on goal, only three of them in the final half of the game. Meanwhile, star Soviet defenseman Viacheslav Fetisov, at age 29 probably playing in his final Olympics, scored a goal just 26 seconds into the game. He later added two assists. Anatoli Semenov and Igor Larionov each scored two goals.

The way the Soviets are playing, they likely would have won the gold medal on their own Sunday. But they got an opportunity to take care of that tonight when Finland was knocked out of a chance for the gold medal by Czechoslovakia, the last-place team in the medal round.

The Finns still are assured of winning a medal Sunday, the final day of Olympic competition. They clinched no worse than a bronze medal when Canada defeated West Germany, 8-1. The Finns can win the silver medal if they upset the Soviets Sunday or if Sweden loses its final game to West Germany.

The Czechs, who won the silver medal in the 1984 Olympics at Sarajevo, had four power play goals while goaltender Dominik Hasek, who has been injured and has not played well here, stopped 24 shots, many from close range.

Igor Liba had two goals, while Jiri Sejba, Dusan Pasek and Vladimir Ruzicka each scored once for the Czechs. Pasek had three assists.

There was to be no upset in the next game. Playing without injured defenseman Alexei Kasatonov, the Soviets never gave Sweden a chance. When Fetisov's shot from the slot slid under the left pad of Swedish goaltender Peter Lindmark before the game was even half a minute old, this had the makings of another Soviet rout.

Surprisingly, Sweden tied the game on a power-play goal six minutes later. Ulf Sandstrom came up with the puck in front of Mylnikov on a pass from Mats Kihlstrom and, falling backward, pushed it past Mylnikov. With just 6:46 gone in the game, the score was tied, 1-1.

But then came the Soviet scoring binge that decimated the Swedes. In 1 minute and 41 seconds, the U.S.S.R. scored three times. Sweden was demoralized. Lindmark went over to the bench and asked to be taken out. After the period, he was.

Larionov scored on a pass from Vladimir Krutov, the Olympics scoring leader with 15 points, on the power play to make it 2-1 with 6:28 left in the period. Sergei Yashin was next when he fired the puck between Lindmark's legs on a pass from Semenov with 5:46 to play.

Finally, Fetisov sent a perfectly timed pass to Valeri Kamensky, streaking over the blue line to Lindmark's left. Kamensky, alone on Lindmark, wound up from the slot and fired a slap shot that blew past the goaltender and into the net.

In the second period, Peter Ahslin replaced Lindmark in goal and played well, making nine saves and allowing only one goal, Semenov's point-blank shot with 5:11 left in the period. But the fact that Lindmark was gone was Sweden's admission of defeat. If the Swedes were to have a chance to beat the U.S.S.R., they knew Lindmark, 31, who has played on Swedish national teams since 1981, had to play the game of his life.

Obviously, he did not.

Larionov and Semenov tacked on third-period goals, and that was it.