Prince William County has made large strides in attracting business in the last five years, but it has failed to significantly improve the crucial balance between commercial and residential development, county officials said yesterday.

Last year, the county had an unprecedented boom in business growth, issuing permits for more than $84 million worth of commercial and industrial projects, according to a report released yesterday. More than 3,500 new jobs bring the total county's work force to about 39,000, with most of the growth occurring in office and retail sectors.

Yesterday, officials credited the growth to Prince William's increasing attractiveness to commercial developers as a market with easy access to Washington as well as to the county's aggressive recruitment of business.

Nonetheless, the report said, residential development expanded just as quickly as commercial, meaning the county's tax base continued to have a relatively poor balance between business and housing.

This balance is important because residential dwellings tend to demand county services that cost more than they pay in property taxes, officials said, while the opposite is usually true of businesses.

About 8 percent of the county's developed real estate is commercial and industrial property, roughly the same percentage as in 1980. Ideally, officials said, this rate should be closer to 25 percent.

"We're a far cry from that," said Dyan Lingle, director of Prince William's Office of Economic Development. About 20 percent of Fairfax County's developed land contains commercial or industrial enterprises, according to county statistics.

Prince William has made better headway in its efforts to employ residents in the county, instead of their commuting to jobs in Washington or elsewhere in Northern Virginia.

In 1980, about 75 percent of the county's working population did not hold a job in Prince William, County Executive Robert S. Noe Jr. said. Although Prince William remains a bedroom community for the majority of breadwinners, this figure has dropped greatly as the total number of jobs in the county has doubled in five years, officials said.

The county received a big increase in its retail employment with the opening of the Potomac Mills Mall in Woodbridge last year, Lingle said. Many jobs also were created for higher-skilled employes, particularly in engineering and other technical fields, she said.