Elizabeth Hanford Dole yesterday announced she would quit the Federal Trade Commission March 9, at least partially to help her husband, Sen. Robert Dole (R-Kan.) in his exploratory bid for the presidency.

The 42-year-old Dole has served on the FTC for five and a half years. Her departure will give President Carter his third appointment on the five-member commission.

Commission Chairman Michael Pertschuk called Dole's resignation "a severe loss to the commission." He called Dole "a pillar of competence" and said "the American consumer owes her a deep debt of gratitude for a job well done."

Dole said her husband will shortly announce the formation of an "exploratory committee" to assess his chances for the presidency, and added that "I will be exploring with him."

She said it would be "difficult" to maintain an appearance of propriety while working both on a campaign and in her role as a commissioner at the FTC.

As for other future plans, Dole said she is considering several options. "I'm looking at the nonprofit area, where I can continue working on issues that I have been involved in at the commission," she said in an interview.

In announcing her departure, Dole praised the commission's increased efforts to foster competition in American industry "through vigorous enforcement of antitrust laws and the education of consumers.

"My philosophy has been that the FTC is a real promoter of the free enterprise system," she said. "The agency has been a force in the deregulation area. We have moved out front and taken considerable steps in intervening in other agency deregulation efforts."

In her letter of resignation to President Carter, Dole said "I leave the commission now more than ever convinced that American free enterprise, for all its shortcomings, still provides the greatest economic opportunities for individual freedom to produce, and in producing, to earn a share of America's wealth."

She said it had been "an honor and a privilege" to serve on the commission since 1973.

Dole said in the interview that her decision had not been made "overnight. There were a lot of conversations with my husband."

In the press release announcing her departure, Dole said the decision to leave "was not an easy one. The commission's sweeping responsibilities cut across nearly all of American industry and thus present a uniquely challenging and rewarding opportunity for public service."

Her replacement cannot be a Democrat, since there are already three Democrats, the maximum number allowable, serving, including Carter appointees Pertschuk and Robert Pitofsky.

Dole was designated as an independent, with no party affiliation.