The House Post Office and Civil Service Committee will vote today on a $9.5 billion package that would aim to gradually close the gap between white-collar pay in the government and the private sector.

Rep. Gary L. Ackerman (D-N.Y.) believes his plan strikes a compromise between his original bill and a less costly White House plan for more selective pay raises and changes.

Most of the committee's 15 Democrats will support the Ackerman bill, which has the support of federal unions. Only one of the committee's nine Republicans, Rep. Constance A. Morella of Maryland, is committed to the bill that would:

Start automatic October raises, beginning in 1991, linked to the Labor Department's employment cost index. The index reflects pay and benefit costs to private employers. Had such a system been in effect this year, U.S. workers would have gotten a 4.2 percent January raise. Instead, they got a 3.6 percent increase based on a political compromise between Congress and the administration. Federal retirees, whose pensions are indexed to inflation as measured by the consumer price index, got a 4.7 percent raise in January.

Establish local adjustments in addition to the employment cost index raise for all employees. The raises would start in 1992 and represent a second tier to the October increase. The local raises would begin the process of a partial catch-up with salaries paid by the private sector locally. Aides to Ackerman said these local adjustments would close the federal-industry pay gap in 10 years or less.

Allow the special 8 percent raise proposed by the president for workers in New York City, Los Angeles and San Francisco. The president also would be authorized to give other special raises to employees in high cost, high salary cities as needed. Morella and Sen. Barbara A. Mikulski (D-Md.) already have introduced bills that would give 8 percent raises to workers in Washington and Baltimore if they are given to employees in any other cities.

Permit the government to establish special occupational pay systems for firefighters, law enforcement personnel and health care workers and to give bonuses of up to 25 percent to recruit or keep key employees.

Allow agencies to hire employees above the lowest step of the salary grade, pay transportation and travel for new employees or job candidates and give time off as an incentive. Health Premiums

The committee today also resumes hearings on changes in the federal health program. It is expected to approve something like the Ackerman health bill that would charge employees $10 per pay period (every two weeks) for self-only standard coverage and $22 for high-option coverage. High-option single coverage would be $20 and family coverage would be $44. For comparison, the popular Blue Cross-Blue Shield plan costs $16.22 per pay period for single coverage and $35.55 for standard family coverage. High-option premiums are $86.68 for single, and $180.91 for family coverage.

The Bush administration opposes the Ackerman bill. The Congressional Research Service has estimated it would cost the government an extra $3.8 billion a year.