WASHINGTON (AP) _ The Supreme Court today let Minnesota state troopers claim the costs of their workday meals as tax deductions.

The justices, without comment, rejected government lawyers' arguments that lower court rulings allowing the deductions ''invited innumerable claims'' by the millions of Americans who eat meals while on the job.

Minnesota State Highway Patrol troopers Karl W. Christey and Steven L. Pillsbury claimed such deductions for the tax years 1981 and 1982.

The Internal Revenue Service denied the claims, but in a subsequent lawsuit seeking tax refunds a federal trial judge and the 8th U.S. Circuit Court of Appeals ruled for the troopers.

Christey had deducted $962.66 and $880.28, respectively, for his meals while on duty. Pillsbury claimed $944 and $968, respectively, for the same years. Both men made their claims under that part of the Internal Revenue Code allowing deductions for ''ordinary and necessary business expenses.''

The Supreme Court in 1977 ruled that New Jersey state troopers could not claim the costs of their on-duty meals as tax deductions, but that case was decided on another portion of the tax code.

Minnesota troopers are required to eat their meals in a public restaurant adjacent to a highway whenever practical.

They must report by radio before beginning their meals, and make sure they supply the telephone number or code number of the restaurant where they are eating.

No more than two troopers may eat together, and they must eat at certain times. They may not bring meals from home.

In its ruling last March 2, the 8th Circuit court acknowledged that the costs of someone's meals most often is a personal expense and not tax- deductible.

But the appeals court agreed with U.S. District Judge Paul Magnuson that ''the number of duty-related restrictions and requirements concerning their meals effectively extended the performance of the troopers' duties from patrol cars on highways to tables in restaurants.''

The appeals court added, ''This is not a case in which the taxpayers are attempting to deduct the cost of their meals merely because they are working overtime, or working through their meal break, or where business activities make meals at home inconvenient.''

In seeking Supreme Court review, Justice Department lawyers said the appeals court was wrong, and that meal costs are personal - not business - expenses.

''The troopers expended these funds because they were hungry, not because the Highway Patrol required it,'' the government appeal said. ''The meals were a personal benefit to them just like the meals that other types of workers consume during the workday.''

The appeal contended that the lower court rulings ''invited innumerable claims for their deduction, depending upon the outcome of an undefined inquiry into the almost infinite variety of circumstances of each person's employment.''

Government lawyers said the appeals court ruling ''encourages substantial factbound litigation, which will have major deleterious effects on tax administration.''

The case is U.S. vs. Christey, 88-1023.