Another high stakes game is under way for the lucrative health business in Northern Virginia, as the Fairfax Hospital Association and a Nashville-based corporation gear up to battle for the right to build a new hospital in western Fairfax County.

The association is expected to announce today at a news conference a master plan for health care in Fairfax County through the year 2000. Part of that plan is a proposal to expand Fairfax County Hospital and to relocate Commonwealth Hospital from its Fairfax City location on Chain Bridge Road to the Fair Oaks Mall area north of the city, where Rte. 50 and I-66 intersect.

The nonprofit association currently runs Fairfax Hospital, Commonwealth Hospital and Mount Vernon Hospital, which gives it a monopoly on hospital facilities in the county.

The Hospital Corp. of America, a for-profit firm that operates 370 hospitals nationwide, is also "very interested" in building a hospital in the western Fairfax area, although it has not settled on an exact location, said executive vice president David G. Williamson Jr.

He said he did not know when a formal proposal would be filed, but that one is in the works. "We have asked our development department to move with some dispatch because others are ahead of us," Williamson said.

The challenge by Hospital Corp. will revive debate over whether the association should continue to be the sole provider of hospital care in the county, whether a for-profit hospital should be allowed in, and whether there are too many hospital beds in the area.

Other groups have tried unsuccessfully to gain footholds in the area because of its affluent, relatively young and well-insured population. The most recent attempt, rejected earlier this year by the regional planning agency and the state health commissioner, was by a Louisville-based corporation, Humana Inc. to build a hospital in Reston.

Before any new hospital is built, the state health commissioner must issue a certificate of need. That decision normally is based on recommendations from the local regional planning agency, in this case the Health Systems Agency of Northern Virginia.

"We do not believe the area needs an additional hospital right now, but we would be willing to consider" any development offer that was combined with an offer to close some other hospital, said Dean Montgomery, executive director of the regional planning agency.

Health planners believe that excess hospital beds cause hospital rates to rise. Northern Virginia hospitals are licensed to operate a total of 2,917 beds, and now operate 2,672. Of the 750 medical/surgical beds operated by the Fairfax Hospital Association, an average of 79.4 percent beds were filled in 1981. Optimum use is when more than85 percent of such beds are occupied, Montgomery said.

Fairfax Hospital has been heavily used, with an occupancy rate of 88.6 percent for its 430 available beds. But Commonwealth filled only an average of 75 percent of its 128 available medical/surgical beds and Mount Vernon filled just 61.1 percent of its 192 beds.

The proposal that Hospital Corp. informally has discussed with the regional agency suggests closing the corporation-owned facilities of Circle Terrace Hospital in Alexandria and possibly Dominion Psychiatric Treatment Center in Falls Church, in return for permission to build the new hospital.

Circle Terrace is in a residential area with no room for growth, Hospital Corp. officials said. The hospital is licensed to operate 127 beds. Those patients could use other hospitals in Alexandria and some or all of the 127 beds could be transfered to western Fairfax under the plan. Dominion has 100 beds.

The size of Hospital Corp.'s proposed new hospital would depend on whether Dominion was part of the package. But if both hospitals are closed, the plan for the new hospital is expected to include less than 227 beds, reducing the total number of beds in the area, Montgomery said.

Hospital Corp. also leases the Northern Virginia Doctors Hospital in Arlington, which it is negotiating to buy. Those additional 270 beds could play a role in the final proposal, Williamson said.

In contrast, according to Montgomery, the Fairfax Hospital Association's proposal to relocate and expand Commonwealth is "distinctly less attractive." Montgomery said that moving Commonwealth "would exacerbate the problem" and the proposal to expand Fairfax "makes no sense" while there are so many excess beds at Mount Vernon.