The Reagan administration hopes to lay the groundwork in Congress this year for a voucher system plan for the federal employe health insurance program.

The program covers 10 million people worldwide, including nearly half the residents of the Washington area -- from senators to retired postal clerks.

The plan may not be included in the president's budget. But administration officials say legislation to put it in effect will be introduced and supported by the White House.

Under the proposal, which Congress has previously ignored, the government would scrap the current system. Uncle Sam now picks up about 61 percent of the average employe-retiree health premium (and up to 75 percent of the premium for postal workers), but in no case does it pay the entire cost.

Under a voucher system the government would issue workers and retirees a single check each year to buy health insurance. The Office of Personnel Management says the checks would be enough to pay the entire premium for a "no frills" health plan. But it has not spelled out an exact amount. Persons who wanted more comprehensive -- and expensive -- coverage would pay any extra premium cost.

Backers of the voucher system say it would encourage the hundreds of plans participating in the federal program -- the world's largest -- to come up with insurance packages that would be attractive and paid entirely by the voucher. They see this as a major first step toward government plans to encourage the health care industry to contain costs and hold down price increases.

People who oppose the voucher system, including most federal unions and some insurance firms, say that it could lull workers into buying inadequate protection.

Current federal health insurance premiums range from about $200 a year to more than $1,600.

The premium for the popular Blue Cross-Blue Shield high-option family plan is $120.88 every two weeks. Of that, the government pays $53.36. Employes pay $67.52. By contrast, the Government Employees Hospital Association plan, also one of the most popular, charges a biweekly premium of $71.25 for high-option family coverage. The government pays the same $53.36 biweekly share, but employes pay $17.89.

The key to the voucher plan is how much the voucher would be for and what system would be used to adjust it upward to keep pace with premiums. Just how that would work will have to be explained before Congress buys the concept.