President Reagan's welfare cuts for working mothers forced many poor families deeper into poverty, according to a study of 207 Georgia welfare families funded by the Ford Foundation and released yesterday by the Center for the Study of Social Policy.

Center director Tom Joe, a welfare official in the Nixon administration, said the 207 families consisted of single mothers who had been working but receiving some benefits under the Aid to Families with Dependent Children (AFDC) program, plus food stamps and Medicaid.

Before the 1981 AFDC changes enacted by Congress at Reagan's request, Joe said, the average family included in the study received $609 a month from earnings, AFDC and food stamps.

The immediate effect of the changes was that families lost their welfare payments, averaging $64 a month. While their food-stamp benefits went up $9 a month, they were left with $554 net. They also lost Medicaid eligibility.

As a result, the proportion of the 207 familes below the poverty line rose from 70 to 79 percent.

"Our findings demonstrate that these mothers were leading an impoverished existence before the welfare cuts and were only pushed further into poverty afterwards," Joe said. "These women clearly wanted to work more but were not able to increase their work efforts to make up for their lost AFDC and Medicaid benefits."

Joe said the result would have been more severe had Georgia not changed its state eligibility rules to counteract some of the president's changes.

For many of the families studied, Joe said, the loss of Medicaid was even more serious than the reduction of monthly income. Many went without medical care, and others built up large debts.

In response to the loss of income, 20 percent of the mothers sought more child support from the absent fathers of their children but Joe reported that few received increases.

Fifteen percent gave up their houses and moved in with their parents.