John Stearns' first home run since August 1979, a two-run homer in the eighth, gave host New York a 5-4 victory over Steve Carlton and the Philadelphia Phillies and a split in their doubleheader last night at Shea Stadium.

The Phillies won the first game, 3-1, on the five-hit pitching of Dick Ruthven and Mike Schmidt's 26th home run.

In the second game, Dave Kingman drew a walk with no outs in the eighth inning. One out later, Stearns hit his first homer in 197 games.

Carlton struck out 15 to break his club record of 14 for a left-hander, which he accomplished four times. His personal high for one game is 19, set with the St. Louis Cardinals in 1969.

Mike Marshall (3-2) was the winner in relief. Carlton dropped to 12-4.

Carlton gave up two runs and three hits in the first inning, but was in control until the eighth.

The Phillies scored a run in the second and then took a 4-2 lead in the third with the help of Gary Matthews' two-run homer. The Mets closed to 4-3 in the fifth when Dave Kingman walked with the bases loaded. It was his first RBI since Aug. 22, when he hit a grand slam against Cincinnati.

In the opener, Ruthven (11-5) struck out four and walked two in earning his first victory over the Mets in four decisions this season. Ruthven snapped a 1-1 tie in the fourth inning against Pat Zachry (7-12) with a single that scored Larry Bowa, who had doubled.

Schmidt homered down the left field line in the fifth.

The Mets took a 1-0 lead in the first. Wilson led off with a single, stole second, moved to third on Stearns' sacrifice and scored on a wild pitch.

The Phillies tied the game in the third when Pete Rose opened the inning with a base hit, advanced to third on Bake McBride's double and came home on Matthews' sacrifice fly.