President Reagan's proposal to eliminate duties on imports from the Caribbean yesterday was greeted with criticism, confusion and some support from Congress and leaders in the sugar industry.

Administration officials had pondered how to help Caribbean countries export more to the United States without further reducing market prices for sugar or affecting the recently enacted sugar price-support program that was debated heatedly in Congress last year.

The administration plan would remove the 2.81 cents per pound duty on sugar exported to the United States from the Caribbean on quantities up to 110 percent of the highest historical import levels. That would limit duty-free sugar imports to about 1.2 million tons.

In addition, there is an import fee currently set at 2.1 cents per pound and trade officials said they were unsure what effect the president's plan would have on that. The fee is imposed to keep imports below harmful levels.

Government trade officials said duty-free treatment should have no adverse effect on sugar prices or the price support program.

But not everyone was satisfied with the administration's assurances.

"The president's proposal to increase the quantity of duty-free sugar imports may disrupt the newly enacted domestic price stabilization program," said Sen. Daniel K. Inouye (D-Hawaii).

He said the plan "is well intentioned, but places an extremely heavy burden on Hawaii, Puerto Rico and the Virgin Islands by disrupting the domestic market for our agricultural products. If we are to extend aid to our Caribbean friends, as I believe we should, then the cost should be shared by the entire nation."

"The duty-free treatment of all Caribbean imports, as well as the marketing assistance to encourage Caribbean exports to the United States proposed by the Reagan administration, will have an adverse effect on Hawaiian pineapple, sugar and papaya sales on the mainland," Sen. Spark Matsunaga (D-Hawaii) complained.

Several cane- and beet-sugar industry leaders said they weren't sure what effect the president's proposal would have on them and they would have to study it before commenting further.

However, Horace Godfrey, who represents Florida and Texas sugar-cane growers and processors, said other sugar exporters such as Australia, Brazil and the Philippines probably will be hurt by the program.