FOR THE PAST two years, the Prince George's County government has had a goal of giving 30 percent of its business to minority-owned firms. The county government again fell short of its goal this year, and has received strong criticism from some black leaders. Is that criticism justified?

The answer is no. County Executive Parris Glendening and his administration have been moving in the right direction, and believe that the 30 percent goal can be achieved -- with more time. First, county officials said they underestimated the number of multi-year contracts already in effect. In fiscal year 1984, county officials said that minority firms received about $4 million in business that ranged from construction to food supplies. In fiscal year 1987, minority firms had a 19 percent share of $92 million in contracts. That's $17 million in business. Part of it is a new five-year contract with the Maxima Corp. of Rockville to provide computer services for the county government. Maxima is the 16th-ranked black-owned business in the nation.

Prince George's County blacks want a larger share of the county's development boom. That's understandable, but an immediate 30 percent is an unusually ambitious goal. Some say that it should be higher. There are 5,762 black businesses in Prince George's, but far fewer that can realistically provide services for the county.

Other efforts must be considered. Prince George's County officials say they have also obtained commitments from developers to give minority firms a 15 percent share in building the PortAmerica Project and Bowie New Town. The county has financed a $700,000 small-business program for women, minorities and the poor. It has helped people such as county resident Alice MacIntosh open her own business -- a shoe store. But that won't create a business that can directly serve county government.

The county government has made substantial progress in developing, encouraging, and funding minority business efforts. It needs time to do more.