The Senate Judiciary Committee began final action on its immigration legislation yesterday with the chief architect, Sen. Alan K. Simpson (R-Wyo.), asking that it be sent to the floor in time for final Senate action before the congressional recess beginning Aug. 2.

To make the legislative package -- a much narrower bill than the House-Senate compromise that died in the last Congress -- more palatable to its opponents, Simpson won approval of an amendment that would make it easier for illegal aliens to obtain amnesty.

But when the committee resumes consideration of the measure on Tuesday, Sen. Edward M. Kennedy (D-Mass.) is expected to offer an amendment to make amnesty automatic.

In the House, Democratic sources said that Judiciary Committee Chairman Peter W. Rodino Jr. (D-N.J.) and Rep. Romano L. Mazzoli (D-Ky.) are working out final details of their own immigration legislation, to be introduced next week, which will be very much like last year's compromise bill.

Among provisions of that bill were an amnesty plan, criminal penalties for employers who hire illegal aliens, a requirement that employers not discriminate against legal aliens, and provisions to help farmers bring in temporary foreign workers.

Simpson's current bill would lessen penalties for employers who hire illegal aliens. It also would reduce the record-keeping requirements for employers.

Employers would not have to keep paper work proving they had checked the alien status of all employes. But if an illegal alien was discovered, the employer would have the burden of proving retroactively that he had checked the documents.

Simpson's bill has no antidiscrimination provision and does not call for automatic amnesty, but it would grant limited amnesty after a special commission determined that the controls were working sufficiently to trigger the amnesty program. His original bill called for a 16-member commission, but his new plan would establish a nine-member panel and all members would be required to support the concept of legalization.

Simpson told reporters yesterday that if legislation is approved in this Congress, it will be an amalgam of a number of proposals being discussed on the Hill. He added that there is still major opposition from special-interest groups, ranging from Hispanics to fruit growers.

"The growers are tough," he said. "There's a constituency out there with sharp teeth, and they'll be right there in full flower."