Heads of several Caribbean nations today commended the broad outlines of the Reagan administration's Caribbean basin policy, but they were less commendatory on the U.S. intent to reduce government aid in favor of private investment.

Leaders of small countries told the fifth annual Miami Conference on the Caribbean they first need massive infusion of governmental aid to increase trade and attract private investment.

Prime Minister Vera Bird of the newly independent country of Antigua and Barbuda, said "none of us disagree" with the Reagan administration position that developing countries "must pull themselves up by their own bootstraps."

"But first we must have the straps by which to pull up the boot," he said. "And we will never have the straps if the order of priority does not place the required aid at the forefront."

Ambassador Thomas O. Enders, assistant secretary of state for inter-American affairs, told reporters that most leaders with whom he met desired some direct aid.

"But there is a difference over last year," Enders said. "Then they just said, 'Send money.' Now we hear talk of self-help . . . The discussions were much more mature this year."

Enders said any U.S. and regional policy must address three concurrent crises--economic emergencies, insufficient employment opportunities and political instability.

While the administration's long-awaited Caribbean policy has not been spelled out in detail, it is known to emphasize investment, trade and aid, in that order. Nor is it any secret that the policy stems from the administration's desire to "draw the line" against communist expansion in the hemisphere.

Six prime ministers and one president were among the 600 representatives of 30 Western Hemisphere nations attending the conference, which has become a major forum for U.S. and Caribbean governmental and business leaders.

President Reagan, who has repeatedly stressed the role of the private sector in accelerating Caribbean development, has chosen Jamaica as the focal point for his new policy. Prime Minister Edward Seaga, the first head of state received by Reagan last year, was a favorite of Reagan's since his conservative forces decisively routed leftist premier Michael Manley in elections in 1980.

"The transfer of resources from developed to developing world is not a one-way flow but a stimulation of trade with significant reverse flows back to the industrialized world in improved trade flows," Seaga said. "In short, aid is not charity; it is business."

Seaga applauded U.S. consideration of a "one-way free-trade area" for most products coming to the United States from the Caribbean and recommended new U.S. tax legislation to stimulate foreign investment.

"The Caribbean basin is faced with a race between development and discontent," Seaga said. "We can either win that race with urgent development or lose it with raging discontent. And we can do it now with the lesser cost of promoting development than with the greater cost of combating discontent."

Meanwhile, the leaders agreed that deteriorating economies in many Caribbean countries demand an immediate U.S. response. Jose Miguel Alfaro, vice president of Costa Rica, a moderate democratic nation that is on the verge of economic collapse, said "yesterday" would not be soon enough for a concrete U.S. explanation of its Caribbean policy.