At least two Harvard construction projects are in danger of not getting the Federal support they expected, as a result of drastic cuts in President Johnson's new budget.

One University official said yesterday that the Education School's chances of getting money for its proposed library construction are "no more than 50-50." He said the Law School now has a "very slim chance" of obtaining federal funds for classroom construction.

The Ed School's request for $1.8 million for its new library has already been approved by the Office of Education, but not funded by Congress. The Law School is in a more precarious position, because it has not received federal approval for its request.

The new budget slashes construction grants available to four-year colleges from $207.4 million to $133 million, a loss of $74.4 million. Funds for graduate school construction have dropped $7 million from $32.5 million to $25.5 million.

Construction of Mather House will not be affected by the cuts, because Mather is being financed entirely from funds raised in the $82.5 million program for Harvard College.

Gund Hall Safe

Another graduate school construction project, the Design School's Gund Hall, will almost surely be safe because its request for $2 million was funded by Congress two years ago. The Design School has just finished raising $4 million on its own, fulfilling the conditions for the federal grant.

But William A. Doebele Jr., associate dean for Development at the Design School, said yesterday that it is his under standing that "the money is on reserve for us."

Chances Reduced

Some construction projects whose fundraising drives are just getting underway had hoped to ask for federal grants, but their chances of success are sharply reduced under the new budget. The Chemistry-Biology building, part of the new Science Drive, faces this problem.

In other areas of education, Johnson is asking for increased federal spending. The President recommended $100 million more in loan funds for undergraduates and $70 million more for graduate students. The total reduction in spending for construction and equipment at the college level, however, is more than half a billion dollars.

Johnson also asked for increased spending on Head Start, programs for the handicapped, and university research.