April L. Young, executive director of Fairfax County's Economic Development Authority and one of the principal architects of the county's commercial success, has announced she is resigning July 24 to take a job with a private development company.

Young, 40, came under fire this year after it was disclosed that the authority had conducted several opinion surveys that included questions touching on politics.

Her resignation comes as public opinion polls indicate growing disenchantment with the pace of economic growth in Fairfax, and as some politicians are talking about curtailing the authority's role in luring business to the county.

Young stressed -- and county officials confirmed -- that she was not forced from her $78,520-a-year job, which she has held since 1982. Yet she acknowledged that public opinion about economic development in the county has shifted, that the county's economy has matured and that "it just doesn't seem like there's a role for me."

One high-ranking county official who asked not to be identified said: "I think she was reading the tea leaves and seeing there's not going to be a lot of action. EDA's not enjoying the same level of popularity it once had."

Young's new employer will be NVHomes L.P., one of the nation's largest house builders, where she will be a vice president responsible for developing a strategy for building moderately priced houses.

She said her compensation with NVHomes will be "substantially in excess" of her current salary, and called the new job "the proverbial offer too good to refuse."

The authority, whose fiscal 1988 budget of $2.5 million is provided by the county, is a semiautonomous agency controlled by seven commissioners. The commissioners are appointed by the county supervisors.

Under Young's stewardship, the commercial and industrial part of Fairfax's tax base increased to 25 percent from about 17 percent in 1982. With the aid of a strongly probusiness political climate, she coordinated an aggressive campaign to market Fairfax to the nation and the world, including several double-page advertisements in The Wall Street Journal touting the county to prospective businesses.

Young and the EDA were sharply criticized last spring after the authority conducted a series of surveys that quizzed county residents about their attitudes toward transportation and development -- the two most highly charged political issues in the Washington suburbs.

Young's letter of resignation, dated June 26, was sent to Charles G. Gulledge, chairman of the authority. Gulledge transmitted the letter to County Executive J. Hamilton Lambert, and wrote that Gerald L. Gordon, the authority's director of administration, would serve as acting director while the commission searches for a permanent replacement for Young.