The new premier of Quebec tonight tried to reassure leading American businessmen that his government is not planning any "policy of nationalization," that his foreign investment policies are "essentially pragmatic," and that his goal of political separtation from the rest of Canada can be accomplished democratically and without turmoil.

In a major speech to the prestigious Economic Club of New York. Rene Levesque invoked the American Revolution and the Declaration of Independence to argue that his nationalist aspirations for Quebec were "comparable enough to your own beginnings that we naturally hope for and expect sympathy maybe, understanding certainly, in American opinion."

Levesque, 54, was in New York City for two days of meetings with financiers - including the chairman of the City's two largest banks. Walter Wriston of Citibank and David Rockefeller of Chase Manbattan - to soothe qualms the investment community may have about his political and economic policies.

Quebec is a major borrower in U.S. financial markets, and there is also substantial American direct investment in the province, the largest in Canada.

A former television commentator and cabinet minister. Levesque assumed power just two months ago when his Separatist Parti Quebecois won a surprising election victory to oust the ruling Liberals.

Curiosity about the new premier made his speech one of the hottest tickets in town. A spokesman for the Economic Club said interest in Levesque was greater than in any speaker since former Russian Premier Nikita Khrushchev appeared before the group in 1959.

The speech did not break much new ground but appeared intended to persuade the audience of 1,000 businessmen that independence for Quebec is a logical outcome of political currents now flowing in the province, and that Levesque himself is committed to moderation, order and pragmatism in his policies and not the economic and political radical that some have accused him of being.

Levesque said the question now is "not whether Quebec will become independent, nor indeed when it will happen, but rather how, in due time. Quebecers can be expected to take full charge of their political affairs."