Congress next week begins writing one of the most important - and also one of the dullest - pieces of legislation it will handle all year: civil service reform.

It has little political sex appeal for legislators seeking reelection, and is a vague and confusing parkage for voters more worried about inflation, high taxes and global hot spots.

President Carter says he must have reform - his reform - to get rovernment moving and make his reorganization meaningful. Backers believe it would shoot new life into the giant, unresponsive bureaucracy, making it easier to hire the best and fire the worst. They promise new incentives for high-paid federal excutives, and new management tools to allow managers to control people running programs that affect everybody in the country.

Opponents of the streamlined procedures of reform argue it would transform the generally apolitical bureaucracy into a political arm of the White House. They say it would make it easier to fire the best, and put experienced career managers and executives under the thumb of political appointees more interested in brownie points than the red, white and blue.

Both the Senate Governmental Affairs Committee and the House Post Office-Civil Service Committee, which handle the bill, have given indications that members would rather work on reform in a nonelection year. But the bill writing starts next week. At least one of the committees may have its version of reform completed before the Memorial Day recess.

After a masterful job if selling the reform package to key members of Congress, the AFL-CIO and other important groups, the White House now will shift to behind-the-scene tactics. Federal unions, executive groups and veterans' organizations who oppose all or parts of the reforms also will be wheeling and dealing with committee members and all-important staffers to have certain items deleted or watered-down.

Antireform legislators plan dozens of amendments when the bill hits the floors of the Senate and House. But it now appears that the Carter administration will get most of the reforms it wants, and certainly more than most observers figured it would get.

For the average U.S. worker, minor shareholders in the world's largest company, the only thing to do is sit back and watch as a busy, politically preoccupied Congress works on the rules and regulations of the outfit most have signed on with for life.