Secretary of State Alexander M. Haig Jr. warned the National Governors Conference yesterday that continued radicalization of countries in the Western Hemisphere could cause an unprecedented flow of refugees to the United States.

Haig was not specific in discussing the source of his concern, which appeared to grow out of the guerrilla conflicts in El Salvador, Guatemala and other Central American states.

He said, however, that a refugee flight based on sudden changes "would make the Cuban influx look like child's play."

Responding to repeated concerns expressed by governors whose states bear the brunt of new arrivals, Haig said the United States must deal "in an enlightened way" with social and economic problems that give rise to refugee flows.

He noted that President Reagan will outline plans for such actions in his speech on the Caribbean Basin later this week.

Gov. Richard D. Lamm of Colorado, who was particularly outspoken, told Haig that a strong reaction against legal and illegal immigration to the United States is growing in the American body politic.

Lamm ascribed the shift in part to high unemployment here.

Gov. Lee S. Dreyfus of Wisconsin urged that, in case of another mass influx, new arrivals be required to meet a test of their "economic viability" before being permitted to bring their families to join them.

He also urged that English language study be given top priority among programs for new arrivals.

Of about 1.5 million illegal immigrants to the United States in 1980, according to Haig, at least half came from Mexico.

He said the authorization for refugee arrivals under legal programs is being reduced somewhat.

State Department officials said about 160,000 people arrived under refugee programs in fiscal 1981, more than 130,000 from Indochina.

The 1982 authorization is 140,000 from all countries, but the arrival rates so far suggest that a smaller number will land, officials said.