The Story of Martha McSteen, the acting commissioner for the Social Security Administration, who may be replaced by a political appointee, is not encouraging to government workers, and that is doubtless okay with Ronald Reagan, who doesn't think much of them anyway.

McSteen, a 60-year old native of Texas, has spent her entire working life in the agency which she has run for 15 months. She began in 1947 in a field office in Kansas, and has been on the rise ever since.

She had received all the awards available to an exemplary civil servant, and her September 1983 appointment in acting capacity was hailed by HHS Secretary Margaret Heckler as a mark of the favor that diligent women federal workers can expect from the Reagan administration.

McSteen has many Capitol Hill admirers in both parties, among them Rep. Jake Pickle of Texas, the Democrat who oversees Social Security matters in the House, and Robert Dole of Kansas, who is now the Republican leader of the Senate.

She has no enemies that anyone knows about. But apart from Rep. Silvio Conte (R-Mass.) she seems to have nobody to go to bat for her. Democrats thought that kind words might spoil her chances; and Republicans apparently thought that merit might carry the day.

Much puzzlement was expressed over the long failure to make her appointment permanent. She was an efficient manager -- and a good soldier. At the time of the administration's brutal review of disability payments -- thousands were knocked off the rolls, and after much anguish and legal expense, reinstated by the courts -- she had prepared testimonu favoring some changes in the process. But, according to Social Security Administration insiders, her remarks were censored by OMB Director David Stockman, and she fell into line with the administration.

Some speculated that the treatment she was receiving could be just another way of the White House expressing its antipathy to career civil servants. Lately, Donald Devine, director of the Office of Personnel Management, has been expressing the need for more temporary workers. And in the puzzlement, many remembered Reagan's lifelong hostility to the Social Security Administration, a popular government program which worked.

Through the years, he has picked at it, wanting to make it ''voluntary,'' trying to cut it back. Just recently, in the heat of the campaign, he was converted to the status of true believer and undying champion. His willingness to keep a ''temporary'' at the helm was seen as a way of diluting accountability and lowering the heat that Social Security unfailingly generates.

Some friends of the program felt that his real opinion of the agency was conveyed through the strange circumstances of the appointment of John Svahn, McSteen's predecessor, who, for a brief time, was both Social Security commissioner and deputy secretary for HHS. It was as if a department with 80,000 employes and a clientele of 40 million senior citizens could be run with the left hand.

Because of poor chemistry between him and Secretary Heckler, Svahn left HHS and eventually, after putting its computer system right, also left Social Security for a White House job. McSteen was made commissioner because she was a professional, and soeone who could be trusted not to make trouble. The fact that she had no political history might have been considered a plus, since there is now talk of making Social Security an independent agency, free of political appointment. But with the White House, it mattered as little as merit.

Rep. Conte once asked a White House witness at a public hearing why McSteen was not named. He got no answer. The speculation was that Svahn might eventually want to have his old job as commissioner back.

But the answer, it seems, was that the White House wanted one of its own in charge. Dorcas Hardy, assistant secretary of Health and Human Services for human development, who once worked for Svahn in the California Health Department in the time of Reagan, was picked for the plum. She is a Reaganite, and ideologue. At HHS, Hardy's conduct was controversial: in making awards, she was said to favor right-wing organizations over those from the left. But that's not the sort of thing that gets you into trouble with the White House.

When reports of McSteen's replacement began to circulate, her press officer advised that she would have no comment. She would say nothing until given permission by the public affairs office of Health and Human Services.

It was probably just as well. What could she say, except possibly that she hoped that other faithful and efficient civil servants fare better.