At last, Congress seems to be on the verge of making a long-overdue change in the nation's immigration laws.

An absurd twist of U.S. policy allows hundreds of thousands of unskilled foreigners into this country, many of whom wind up on welfare rolls, while denying entry to many potential immigrants who possess skills that America needs.Current law places heavy emphasis on family unification, letting in relatives of recent immigrants who have gained permanent residency status. This results in large numbers of poor people, frequently with little education or occupational training, arriving from Latin America and Asia. Immigration from European countries, which used to be the main source of new blood for America, has slowed to a trickle.

Only about 4 percent of U.S. immigrants are admitted on the basis of skill levels alone. The figure in Canada is 25 percent and in Australia 50 percent. Thousands of highly skilled people - scientists, engineers, computer specialists, medical technicians and the like - want to come to America, where many jobs needing their talents are going begging, but they cannot get visas.

The bill that Congress is now on the verge of adopting makes better sense. Under it, some 420,000 workers, professionals and members of their immediate families would be admitted to the United States in the next three years because they possess needed skills. Of these, 36,000 would be employees of American companies in Hong Kong. Pressure for emigration is increasing in the British colony as the time nears for it to be turned over to China in 1977.

In 1995 and afterward, the new bill also provides for 675,000 visas, including 480,000 for relatives. The number admitted to bring in additional skills would continue at 140,000 a year - more than double the present 60,000.

The upshot should be to further the national interest coordinating immigration policy more closely with U.S. needs.