If President Reagan looks a little sheepish Monday when he hands out $20,000 bonuses to 38 outstanding civil servants, it will be because the highly touted awards are worth only about 50 cents on the dollar.

To be precise, the $20,000 bonuses will shrink to $11,130, before taxes, because of a law that limits the amount of pay and awards that career government workers can get in any one year.

The situation could be particularly embarrassing for this administration, which many of the government's 2.8 million employes consider to be anti-bureaucrat.

Officials in charge of the Rose Garden ceremony, to honor and reward with $20,000 and $10,000 bonuses the best and the brightest in the Senior Executive Service, hoped the presentations -- which are to be videotaped and shown to feds everywhere -- would help ease some of the cold war tensions that have arisen between the career federal staff and this administration.

For the past 22 months, many feds have suffered from tension headaches. The tension was brought on by RIFs (layoffs) and payless furloughs (some caused by congressional budget foulups) that have cost many people their jobs and meant loss of income for many more.

Congress and the administration also temporarily cut future retirement benefits for many, and -- beginning Jan. 1 -- will force federal workers to pay the Medicare tax.

Unfortunately, Monday's ceremony may be somewhat dimmed from a financial standpoint. That is because the law limits pay for members of the SES to $58,500. Other laws prevent them from getting combined pay, awards, etc., from the government in any one year exceeding the $69,630 salary of cabinet officers.

Because of the limit, the big awards that will be given to SES members ranked as "distinguished" will be cut almost in half. The 161 SES members who get the title of "meritorious," which carries a $10,000 bonus, will get their full reward, less what the IRS takes.

Nobody is knocking the awards. Nobody is likely to refuse one. It is a high honor and, for the distinguished executives and their families who will personally meet the president, the thrill of a lifetime.

But it is a rather sad commentary on the government's executive pay situation when Uncle Sam can't pay the full amount of the top bonuses that Congress and the Carter administration set up to honor the nation's best civil servants.

Ironically, President Carter was stung a bit the first time he presented the cash to SES people. A couple of weeks after the ceremony, two winners of the big checks -- designed in part to make government service more attractive -- quit their jobs to take better-paying positions in the private sector.

After those highly publicized "defections," some people suggested spreading payment of the awards over a period of time, to keep anyone from taking the money and running. But it was decided that the law was intended to reward people for past excellence, not lock them into their jobs with golden handcuffs.

"I don't want to say that this thing the SES bonus awards ceremony is jinxed," an official said, "but there do appear to be some bugs in the program."