The Children's Defense Fund charged yesterday that although "poverty is the greatest child-killer" in America, the Reagan administration "has targeted poor children and families" for $5.2 billion in budget cuts in fiscal 1986.

Marian Wright Edelman, president of the nonprofit child-advocacy group, said the budget "emasculates low-income housing," tears another "hole in the tattered survival net of Aid to Families with Dependent Children," which is the major income-support program for about 7 million poor children, and cuts Medicaid and child-nutrition programs.

Edelman released a children's fund analysis showing that under the president's proposals, programs for children and their families would total $69.2 billion in fiscal 1986, or $5.2 billion less than would be spent if current policy remained unchanged.

From 1986 to 1990, the new cuts would total $37.6 billion, according to the analysis.

The biggest 1986 cuts would be in Medicaid, $1.1 billion; student financial aid and loans, $1.7 billion; social services and community services grants, nearly $400 million; the Job Corps, legal services and youth employment, $1.1 billion; and child nutrition and other food programs such as the special feeding program for women, infants and children, $726 million.

The analysis also estimated that per capita spending for low-income families in constant 1985 dollars, which was $489 in 1981, would drop to $396 by fiscal 1990 as a result of past and current Reagan proposals. Over the same period, the fund said, defense spending per capita was estimated to rise from $806 to $1,419.

Using figures developed by the government of the state of Maine and released in 1983, the fund declared that "10,000 American children die each year from poverty. This compares to 8,000 child deaths from traffic fatalities, 3,000 from cancer, 1,800 from heart disease and 1,200 from suicide."

Fund officials said the Maine figures had been computed by comparing the death rates from 1976 to 1981 of Maine children under 15 who participated in welfare programs with those of non-welfare children. The Maine study found that poor children are three times more likely to die than non-poor children, the officials said. The excess of deaths among poor children was then projected nationwide, they said.

Edelman said the study found that from 1985 to 1990, a total of 22,000 American babies would die primarily because of low birth weight, but at least one in eight could be saved from death, and many others from handicapping conditions, if their mothers received prenatal care.