WASHINGTON (AP) _ Senate Majority Leader Robert J. Dole, R-Kan., gave arts supporters little to cheer about Monday when he said he takes a dim view of the charitable deduction for taxpayers who do not itemize gifts on their federal income tax returns.

President Reagan has asked Congress to repeal the charitable deduction for non-itemizers, who are entitled to deduct one-half of their donations this year and all donations next year. More than half the members of the House are sponsoring a bill to block repeal of the provision, which is scheduled to expire after 1986 unless Congress extends it.

Charitable organizations estimate that repeal will cost them as much as $6.5 billion annually in donations.

Dole, a former chairman of the Senate Finance Committee, told a conference of the American Council for the Arts, a non-profit advocacy organization, that ''I have some problems'' with the charity deduction for non-itemizers, in part because ''it seems to me it doesn't generate that much giving.''

''There is much dispute how much people in the lower tax brackets concern themselves with tax savings as incentives for giving in the first place,'' he said.

The senator also questioned whether Reagan's proposal to reduce income tax rates under his ''tax simplification'' plan, with a top rate of 35 percent instead of 50 percent for the wealthiest taxpayers, would affect charitable giving. Spokesmen for charitable organizations estimate that such a move would cost an additional $4 billion in charitable giving.

Dole said ''we haven't had any disastrous effects on charitable giving'' as a result of lowering the top tax bracket from 70 percent to 50 percent, but ''we're not certain yet what the impact is'' if it is reduced to 35 percent.

''I don't see that impact, but it could be there because, obviously, some charitable giving is tax-motivated,'' he said.

Dole said it was virtually impossible for Congress to pass some sort of tax overhaul bill, ''a very controversial piece of legislation,'' this year.

At a panel discussion on arts financing, Eugene C. Dorsey, president of the Gannett Foundation, said foundation support of the performing arts is beginning to decline as demands for money for social services increase, as a result of Reagan administration budget-cutting.

''It isn't a choice of guns or butter,'' Dorsey said, ''but it may be a choice between Bartok or bread, Shostakovich or shelter, art appreciation or job development, and the choices are not easy.''