New York City Opera general director Beverly Sills, pointing to a "money crisis" in the arts because of Reagan Administration budget cuts, said last week, "I have to be optimistic" that corporations will assume a larger share of the burden of supporting the arts.

Sills' optimistic note was sounded at a day-long forum at the Congressional Club on consumer issues at the Capitol Hilton sponsored by the Atlantic Richfield Co.

Referring to administration plans to slash the funding of the National Endowments for the Arts and the Humanities, she said, "There are hard times coming and we need all the help we can get."

Sills, a member of the Presidential Task Force on the Arts, said she opposed cuts of the magnitude proposed by the administration and had joined the task force to speak out in behalf of the arts as the "signature of a civilization."

She cited figures from the fifth Business Committee for the Arts survey of national corporate giving to the arts which showed corporate contributions have increased from $22 million in 1966 to $436 million in 1979. This compared to the $2.3 billion received from private contributors and $154 million from the National Endowment for the Arts.

The Reagan administration, as part of its economic program, has proposed reductions of nearly 50 percent in the funding for the two endowments, and has urged corporations, foundations and individual contributors to compensate for the decrease in government funding.

Under the new tax law corporations are permitted to contribute 10 percent of their gross income before taxes compared to the 5 percent previously allowable.

According to task force member and National Symphony board chairman Leonard Silverstein, the new law may act "as a depressant . . . many companies will find themselves in a zero taxable position because of the new rules and to contribute a dollar will cost them a dollar.

"Corporations need to be interested in proliferating their image as the good corporate citizen," he said.

The National Symphony's money problems, Silverstein said, are compounded by Washington's lack of an corporate base and endowment comparable to that of the New York or Pittsburgh orchestras.

This, he said, "puts pressure on charitable recipients to demonstrate their worthiness as an organization."

His remarks suggested that carefully executed fundraising drives may initially bring in money essential to the orchestra's survival, and they may also provide the justification for long-term corporate investment programs designed to enhance a company's public image.