After trying for four years to revamp the government's seniority-dominated layoff rules, the Office of Personnel Management has softened its stand. It is about to issue guidelines that place more emphasis on job performance when reduction-in-force decisions are made, but at the same time don't devalue the length of service as much as originally proposed.

In drawing up the regulations, OPM has agreed to make changes in the "point" system -- based on length of service and job performance -- used by agencies to decide who is kept and who is fired during RIFs. OPM will withdraw a pending proposal that would have greatly watered down the government's last-hired, first-fired layoff system.

Agreement on the regulations was reached after the primary congressional critics of OPM's original plan accepted some changes in the seniority-based system of layoffs.

The agreement was reached between Reps. Steny Hoyer (D-Md.) and Frank Wolf (R-Va.) -- whose districts are heavily populated with federal employes -- and OPM's new director, Constance Horner.

Officials of the personnel agency refused in interviews yesterday to outline details of the new RIF proposals, but said they had found "persuasive arguments" for modifying their earlier plan. Meanwhile, Hoyer and Wolf have agreed to withdraw their proposal for a congressional ban on changing the RIF rules.

Under former director Donald J. Devine, OPM had sought for four years to initiate a new RIF rating system that would give more weight to annual job performance ratings.

Under the various systems proposed by OPM -- and blocked by Congress -- longtime employes with "fully successful" job ratings could have been fired ahead of workers with less service time and better ratings of "exceeds fully successful" or "outstanding."

During the first 3 1/2 years of the Reagan administration, about 2,900 federal employes in this area were fired because of budget cuts or reorganizations. Women's organizations and civil rights groups complained that a disproportionate number of those fired were women or minority group men who lacked seniority.

OPM proposed a system that it maintained would give greater job protection to women and minorities by assigning more value to performance and less to seniority.

But unions opposed OPM's proposed new rules, arguing they would make it easier for bosses -- for political or personal reasons -- to get rid of long-time workers by giving them bad job ratings and then conducting a RIF. And on several occasions, Congress banned OPM from putting any new RIF rules in effect.

OPM was proposing that employes be given one point for each year of service and 20 points for an "outstanding" rating, 16 points for an "exceeds fully successful" rating and 10 points for a "fully successful" rating. Performance points would have been averaged over three years and then added to the employes' seniority points. Workers with the lowest point totals would have been fired first.

Hoyer had pressed OPM for more employe and union involvement in drawing up RIF guidelines. Wolf insisted on special protection for employes with at least 12 years of service. OPM wanted more value given to job performance.

"I can't give you any details," a congressional source said, "because the lid is on this one tight until Hoyer, Wolf and OPM can make an announcement. But obviously all sides think they got pretty much what they wanted, or there wouldn't be an agreement."