The Chicago White Sox battered Baltimore pitchers for 26 hits, the most ever against a modern Oriole team, in an 18-5 rout today, then made it a doubleheader sweep as Harold Baines' two-run single in the fifth inning lead a 5-3 victory.

In defeat, Ken Singleton hit two home runs in the first game and one in the second. He batted in five Oriole runs.

In the opener, Chet Lemon drove in four runs and Bill Almon and Greg Pryor batted in three each as four Baltimore pitchers, including loser Scott McGregor in his first 1981 start, were victimized. The 26-hit yield exceeded the previous high of 24 given up the Orioles in a June 1978 loss to the Toronto Blue Jays.

In the second game, Baltimore reached White Sox starter Francisco Barrios early, scoring twice in the first inning as Singleton drove a run across with a grounder and John Lowenstein delivered another with a single.

Chicago got the runs back just as quickly in with bottom of the first. Tony Bernazard singled with one out and scored after Lamar Johnson singled and Baltimore shortstop Wayne Krenchicki threw wildly to the plate. Johnson took third on the play and tied the game, 2-2, when he scored on Wayne Nordhagen's single.

Singleton gave the Orioles a 3-2 lead in the third when he clouted Barrios' 2-2 delivery into the lower left field seats for his third home run and fifth RBI of the day.

But Baines' double gave the White Sox a 4-3 lead and Chicago scored an insurance run in the sixth on Jim Essian's double.

Barrios (1-0) yielded seven hits in 6 1/3 innings, walking two and striking out one in his first victory in almost a year. Kevin Hickey worked one-third of an inning of relief before Ed Farmer finished up, notching his second save.

Baltimore's Steve Stone (1-1), the 1980 Cy Young Award winner, gave up six hits, walked four and struck out two in six innings.

In the first game, the White Sox scored seven runs in both the fourth and sixth innings, sendin 12 men to bat in each inning. Lemmon, who finished with four hits, and Almon, who also had four, each collected a pair of RBI with singles in the fourth inning as Chicago broke a 3-3 tie. Pryor picked up two of his three RBI with a single in the sixth.

Right-hander Richard Dotson yielded three RBI and a pair of 400-foot homers to Singleton, but survived a rocky start to even his record at 1-1. He gave up seven hits, struck out four and walked four in going the distance for the first time this season.

Meanwhile, results of a blood test on Eddie Murray cleared the way for the first baseman to return to action with the Orioles. Dr. Leonard Wallenstein, the club physician, said the test in Baltimore showed Murray's blood count was normal. Previously, X-rays indicated nothing wrong with Murray's chest, abdomen, nasal passages or neck muscles.

The young slugger has been bothered in recent weeks by chest pains, headaches and a nosebleed, and has spit blood on occasion.

Wallenstein said Murray probably was suffering from a viral infection. If he feels all right, Murray could resume playing Saturday when the Orioles opens a home stand against the Boston Red Sox.