Congress returned yesterday to a major bill that failed last year, a revision of the nation's immigration laws that has been a source of lengthy controversy sharpened by economic hard times.

The bill, which passed 80 to 19 in the Senate last year but died in the House, is the first major amendment of immigration laws since 1965.

An effort, its sponsors say, to regain control over the nation's borders, the bill would grant amnesty to several million illegal aliens already in the country, but then limit to 425,000 the number of non-refugee immigrants who could enter the country each year.

It would also impose sanctions on employers who knowingly hire or recruit illegal aliens, and would beef up the border patrol.

These seemingly simple provisions became one of the most controversial non-budgetary bills before the Congress last year, creating new and unusual alliances among some interest groups while making one-issue adversaries out of others normally on the same side.

The NAACP, for instance, supports the sanctions provision for fear that American workers, especially blacks, are losing jobs to foreigners. Organized labor also supports the provision.

Hispanics and the U.S. Chamber of Commerce oppose it, however. The Hispanics say sanctions would leave employers reluctant to hire anyone who looks Hispanic or foreign. The chamber says checking on the status of workers is the government's job, not the private employers'.

If sanctions are imposed, agricultural growers say, there should also be streamlining of the often-cumbersome guest worker program that grants short-term visas to aliens hired for temporary jobs--jobs the employers say Americans will not take.

"It is an issue filled with emotionalism, guilt and racism," said Sen. Alan K. Simpson (R-Wyo.), sponsor of the bill and chairman of the Senate immigration and refugee policy subcommittee, which opened three days of hearings yesterday. "It's just fear of somebody who's foreign," he said.

But some of yesterday's opening testimony dealt more directly with competition for jobs.

"At a time when unemployed Americans are standing in lengthening soup kitchen lines or in lines to receive a small block of free government cheese, I do not believe that we can in good conscience continue a policy permitting almost completely open borders," Sen. Walter D. Huddleston (D-Ky.) told the subcommittee.

Huddleston said that government policy was forcing 14 million out-of-work Americans to compete with foreigners for jobs. "The only conclusion that can be drawn from this is that this government is concerned more about the welfare of foreign workers than it is for its own unemployed," he said.

Sen. Paula Hawkins (R-Fla.) blamed many of the 120,000 Cubans who came to Florida as part of the Mariel boatlift in 1980 for increased crime in south Florida, which she said is prompting many residents to move northward.

The bill now before the subcommittee is identical to the one passed last year. Sen. Edward M. Kennedy (D-Mass.), ranking minority member of the subcommittee, voted against that bill. This year, Kennedy already is seeking compromises in areas that were problems last year, according to a Kennedy aide on the subcommittee.

Rep. Romano L. Mazzoli (D-Ky.), sponsor of last year's leading House version of the bill, said yesterday that he believes prospects for House passage this year are better than last, but admitted they remain uncertain.

"Windows have a way of opening around here," Mazzoli said, "and windows have a way of closing."