In what is becoming almost a macabre midsummer spectacle, the American League found yet another unlikely way to lose the All-Star Game tonight, 7-6, when Ron Guildry walked Lee Mazzilli with the bases loaded and the score tied in the ninth inning.

The National league, winning for the eighth straight time and the 16th in the last 17 games, broke a 6-6 tie in the final inning of an exciting if sloppy game on four walks and not a solitary hit.

Reliever Jim Kern, who allowed a 320-foot Kingdome opposite-field homer to Mazzilli in the eighth that tied the game, 6-6, walked three men in the ninth (one intentionally) before giving way to Guildry, the 1978 AL Cy Young Award winner, with the bases jammed and two outs.

Mazzilli already had been a discount hero when his dinky fly ball fell into the first row of seats in the short left field corner the inning before. This time, the New York Met switch-hitting hot-dogging outfielder stepped to the right side of the plate and drove in the winning run without swinging the bat as Guidry, unaccustomed to relief work, walked him on five pitches.

Cohero for the proud National League was right fielder Dave Parker, who threw out two runners - Jim Rice trying to stretch a Parker-misplayed bloop double into a triple to open the seventh, and Brian Downing at the plate in the eighth when he tried to score on a single.

That second throw, helped by a magnificent block of the plate by catcher Gary Carter, took the wind out of the AL for good as the play killed what would have been the goahead run.

Perhaps a contest that had Morganna, the Kissing Bandit, waddle to home plate to kiss George Brett in the first inning, and saw the San Diego Chicken generally make a pest of himself throughout, should have an MVP, as Parker was voted, who got only one infield scratch hit.

It certainly was not a scratch throw that cut down Downing.

The score was tied and two ALers on with two out. Graig Nettles poked a single to right that seemed certain to score Downing from second, especially after Downing got a good jump and was well past third before Parker touched the ball.

But Parker put his whole 6-foot-6, 240 pounds into a blistering throw that arrived at the plate a split second before Downing. Carter finished the glorious play by blocking his fellow catcher off the plate with a hip. Downing hasn't touched the plate yet.

After that goal-line-stand of a play, the end seemed certain. The AL had fought well: scoring three in the bottom of the first to take a 3-2 lead, twice more with rallies in the third and sixth. But how long can the AL, burdened by its memory of failure, stand up to the constant NL pressure?

That Mazzilli pinch-hit homer to start the eighth - a homely 320-foot thing that only the Kingdome could embrace - took most of the starch out of the perennial losers. Parker's throw did the rest.

When Joe Morgan walked with one out in the ninth, the dam started BREAKING AS KERN, FLUSTERED, BALKED HIM TO SECOND, THEN INTENTIONALLY WALKED PARKER. WHEN, WITH TWO OUT, KERN ALSO WALKED LARRY PARRISH TO LOAD THE BASES, AL Manager Bob Lemon called on Guidry, the man who never failed him in last year's classic Yankee comeback for a world title.

This time Guidry was stiff and wild high. On "ball four" he simply slumped forward on the mound in disgust.

Guidry, like his league, already knew the last act. They saw it last year. For the second season in a row, Bruce Sutter of the Chicago Cubs, the fellow with the almost uhittable split-finger drop, got the victory, this time with two final shutout innings of relief. In the ninth, he fanned Rice and Rick Burleson to end with a flourish.

"I didn't have nothing when I came in and I said so to Graig (Nettles)," said the disgusted Guidry. "I'm still recuperating from pitching on Sunday . . . yeah, I'm both tired and disappointed, but disappointed first. This is the lowest position you can reach, coming in and walking a guy in that situation," said Guidry, who was 25-3 last year and is 6-7 this season.

This game was a bit of vindication for Manager Tommy Lasorda, whose Dodgers are 17 1/2 games out of first, prompting Lasorda to say before the game, "When we're in New York, I walk the streets a lot. I'm hoping somebody will kill me."

He made the right moves tonight. "I'd have kept Parker in the whole game if it had gone 20 innings," he said. "As for Sutter, there's no man on earth I'd rather have in that situation."

Until the final decisive acts, this game was exactly the slugfest that had been predicted for the tiny Kingdome, which is called the Bat Cave. Tonight's nine extra-base hits were one short of the All-Star Game record.

This game started with a bang as both starters, Nolan Ryan of the AL and Steve Carlton of the NL, were shelled in a hurry.

After fanning the first two of the game, Ryan walked Steve Garvey, then saw Mike Schmidt and George Foster bang an RBI triple and an RBI double to the opposite field, respectively.

The AL answered immediately. With one out in the first inning, exotic dancer Morganna, a female of striking imbalance, rushed the plate to buss Brett. Perhaps Carlton's feelings were hurt - he never was the same.

Brett walked, Don Baylor doubled him home and Fred Lynn showed off his new 1979 power by homering deep to right - the only bonafide fourbase blast of the night. Lynn, playing with a groin pull, left the game in the second.

The heavy hitting never stopped as the NL pushed home runs in the third and sixth after leadoff doubles by Schmidt and Dave Winfield.

This was the night when the AL continually looked gift horses in the mouth. Schmidt handed them a run in the third with a two-out throwing error. And two big NL rallies died when Bob Boone and Pete Rose, setting a record for playing a fifth position (first base) in an all-star game, grounded into double plays.

But the American Leaguers were capable of sinking to the situation. In the sixth, Reggie Jackson, Brett and Baylor came to the place with a total of eight men on base in that frame. They drove home nobody.

Perhaps that should have been expected of Jackson. He left his Yankee uniform in Oakland and it arrived only in the last hour before game time. He even had a pregame team picture taken in a Seattle Mariner uniform. "I knew Reggie wanted to be traded," said one ALer, "but I didn't know he'd actually go get another uniform."

Each year the American seems to come closer in this game, scaring the National a bit more each time, forcing the contest into its late-inning pressure points.

However, when a leadoff man like league MVP Rice, is handed a bloop double, yet runs into an out, that's win baseball. When the Cy Young pitcher in the loop, like Guidry, walks in the winning run with the bases loaded, that's mysterious jinx baseball.

If this annual July embarrassment doesn't end soon, Jackson may not be the only American League player who shows up without a uniform to identify him. CAPTION: Picture 1, National League catcher Gary Carter keeps Brian Downing from the plate as Dave Parker's great throw from right field cuts down the American League player with score tied in eighth. AP; Picture 2, Phillie mates Mike Schmidt, left, and Larry Bowa double-team Roy Smalley's pop fly, tough to follow in Kingdome. AP; Picture 3, Dave Parker is the All-Star Most Valuable Player.