The American Bar Association voted unanimously yesterday to give appeals Judge Anthony M. Kennedy its top rating of "well-qualified" for confirmation to the Supreme Court.

The endorsement by the ABA Standing Committee on the Federal Judiciary gave the 51-year-old Sacramento, Calif., jurist an important boost six days before the Senate Judiciary Committee is scheduled to begin hearings on his nomination.

The 15-member committee's seal of approval was in marked contrast to its sharply divided vote in September on Judge Robert H. Bork, President Reagan's first nominee for the vacancy created by the retirement of Justice Lewis F. Powell Jr. Bork was rated "well-qualified," but five committee members dissented. His nomination was rejected by the Senate in October after a prolonged and bitter battle.

Judge Douglas H. Ginsburg, Reagan's second nominee for the vacancy, withdrew after acknowledging that he occasionally smoked marijuana while a professor at Harvard Law School in the 1970s. The ABA did not act on his nomination before he withdrew.

Sen. Orrin G. Hatch (R-Utah), who criticized the ABA's appraisal of Bork as "politics," said yesterday's vote was "the way it should have come out and I'm happy for it. We made it clear that if the vote was anything less than unanimous 'well-qualified,' we want all the members of the {ABA} committee to answer why. That got the system back on track and away from politics."

The Justice Department announced the ABA's action, and Justice spokesman Terry Eastland called it "good news. Obviously Judge Kennedy merited this rating. This is just another reason why he should be swiftly confirmed."

With no broad-based opposition to Kennedy having surfaced, the confirmation hearings are unlikely to see the divisive ideological battle that characterized the three-week-long battle over Bork.

No senators have announced they will vote against Kennedy, and of the numerous liberal groups that successfully opposed Bork, only the National Organization for Women has said it will oppose Kennedy.

Judiciary Committee staff members yesterday counted fewer than 30 requests from people or groups wishing to testify -- versus more than 200 requests received before the Bork hearings.

Kennedy is scheduled to appear Monday and Tuesday, with the hearings "ending perhaps as early as Wednesday but more likely Thursday," said Pete Smith, spokesman for committee Chairman Joseph R. Biden Jr. (D-Del.). Biden has scheduled a vote on the nomination shortly after Congress returns from its winter recess in late January.

Under the ABA guidelines, a "well-qualified" rating means the nominee "is among the best available for appointment to the Supreme Court." A "not opposed" rating means that the nominee, "while minimally qualified, is not among the best available" and a "not qualified" rating means the nominee does not meet the ABA's standards for professional competence, judicial temperment and integrity.

Civil rights and civil liberties groups reacted cautiously to the ABA endorsement.

Nan Aron, executive director of the Alliace for Justice, a group that opposed Bork, said that "while the favorable rating will be considered by the committee, it is the committee's responsiblity to advise and consent and to consider Kennedy's entire record. That's what these hearings are about and we hope the committee performs its task in a responsible fashion."

Ralph G. Neas, executive director of the Leadership Conference on Civil Rights, said the coalition "is still reviewing Judge Kennedy's entire record and we look forward to hearing the ABA's testimony. But given the fact that so little is known about Judge Kennedy's judicial philosophy, by far the more important witness before the committee will be Judge Kennedy."

An aide to committee Democrats, who asked not to be identified, said the ABA's "rating was not unexpected. It will have the effect of confirming their {the committee members'} preliminary judgment that he does fit the ABA's criteria of qualification."