A major government welfare experiment shows that rates of divorce and family dissolution jumped sharply when the government started guaranteeing a minimum income to poor families.

Researchers told a Senate Finance subcommittee yesterday that black families participating in the famed Seattle-Denver income-maintenance experiment averaged 61 percent more marital breakups than similar families in a control group.

Among white families, the average was 58 percent more breakups than in a control group of white families. Only among Hispanic families was there little difference overall.

These findings, contradicting the Popular notion that income guarantees would insure the stability of poverty families, were spelled out yesterday by Robert Spiegelman of the Stanford Research Institute, project director of the Seattle-Denver experiments, which began in the early 1970s.

The study, financed by the Department of Health, Education and Welfare, is designed to learn how a guaranteed income affects the work habits, family status and other behavior of these who receive it. President Carter's welfare revision bill is based partly on some of the findings.

Michael Barth, deputy assistant secretary of HEW for income security policy said in a later telephone interview that some of the findings "are truly puzzling," especially one showing a higher proportion of marital breakups among couples in the least generous experimental plan than in the most generous.

He said, however, that the administration's welfare revision proposal differs from the Seattle-Denver experiment in several respects. The experiment, for example, has no jobs program or work requirement, both of which are in Carter's proposal.

The study said, in effect, that by guaranteeing many low-income women a minimum income even if they became separated from their mates, the experiment allowed the family to break up.

Without the income guarantee this would be impossible for many women because their husbands were their only source of income.

Wives already earning or cable of earning their own living were the ones least likely to become separated when given a minimum-income guarantee. "The most dependent wives" were the ones most likely to leave when given a minimum-income guarantee.

Spiegelman said the study involved families of different sizes who were given government welfare income guarantees of 90 percent, 125 percent and 140 percent of the poverty line. The current poverty level is $6,200 for a family of four but was less when the study began.

Participants weren't required to work, but if they chose to do so, their welfare payment was cut back either 50 percent or 70 percent. Here is what the study found:

Black families at the 90 percent income guarantee had a 67 higher rate of martial dissolution than a similar low-income black-family control group. At the 125 percent income guarantee, black families had a 93 percent higher family dissolution rate than the control group, while at a 140 percent higher income guarantee a 21 percent higher dissolution rate. The overall black-family dissolution rate was 61 percent.

For whites, the dissolution rate for families at the 90 percent-of-poverty guarantee was 96 percent greater than the control group; for the other two income-guarantee groups, 55 percent and 12 percent greater, respectively. The overall rate for white families was 58 percent more than the control group.