WASHINGTON (AP) _ The government will not force Head Start centers to use a new test to measure how much children learn in the $1 billion program for poor pre- schoolers, a federal official said Thursday.

The Head Start Measures Battery will be strictly voluntary with an aim of helping teachers enhance how much children learn, said Allen Smith, a research specialist in the Department of Health and Human Services.

But the test was sharply criticized by Asa G. Hilliard III, a Georgia State University professor of urban education, who charged it ''is not culturally appropriate for black children'' and would do nothing to improve instruction.

John Bergan, a University of Arizona education professor who helped devise the test, said, ''A vision of development is not enough. You have to have accurate measurement to avoid being seriously misled.''

The Head Start test came up for debate during a workshop at the 15th annual conference of the National Black Child Development Institute, an advocacy group of social workers, educators and community activists.

Head Start, launched 20 years ago in the war on poverty, provides early childhood education, nutrition and health services for 448,250 poor children up to age 5.

Smith said 16,000 Head Start children took the test last year, and 24,000 will be taking it in 225 programs this year.

Initial results indicate the testing may be leading to bigger gains in children's progress from the fall to the spring, Bergan said.

President Reagan declared Head Start an integral part of the ''safety net'' at the start of his administration and has never tried to cut its budget.

But critics complain that the program serves only 20 percent of the eligible children, which Hilliard called ''criminal.''

Bergan said the test - in language, math, perception, pre-reading, social development, and nature and science - is offered in both Spanish and English.

Hilliard said that ignores ''the fact that we have a number of black languages. Translating it into Spanish doesn't help us one bit.''

Smith said the test got off to a ''very rocky'' start, in part because it was too long. But it has been shortened and is now well received, he said.

Eight million children have been enrolled in Head Start since its creation. A recently completed study of all the research on the program concluded, ''children enrolled in Head Start enjoy significant immediate gains in cognitive test scores, socioemotional test scores and health status.''

But that review, carried out by CSR Inc., also found that in the long run the Head Start graduates' test scores do not remain above those of disadvantaged children who did not attend Head Start.

The challenge now is to look for ways to help poor parents sustain the momentum their children acquire in Head Start, Smith said.