Christmas approaches, and so do the final weeks of prison for the last Watergate figure to remain in jail-John N. Mitchell, the former attroney general, who wouldn't cry "uncle" under pressure or become part of some uplift movement to atone for his mistakes.

Mitchell is scheduled to be released Jan. 19 after serving 19 months. H. R. (Bob) Haldeman was released yesterday, after 18 months. John Ehrilichman was freed on April 27 after doing 18 months.

A cluthc of lesser figures in the Nixon administration did far less time, with the exception of that audacious adventurer, G. Gordon Liddym who seemed to take great pleasure in prison pain, and managed to convince the feds that he needed at least 52 months.

Anyway, it is probably fitting that this sad, bizarre episode comes to an end during the holiday season when we go about wishing each other well. Watergate shook the lives of many souls who labored for Richard M. Nixon. There were great great strains on families, even divorces. Books, most of the second-rate, were quickly produced and hawked. Several leading characters got into the Jesus business and can still be seen on late-night evangelical shows, telling ot their conversions and warning the young to avoid such perfidy.

Ehrlichman grew a beard, became chummy with Allen Ginsberg (whom he once stalked), Norman Mailer and Marlon Brando-none of whom he ever dreamed of befriending when he sat in the White House. He left his wife, married a younger woman and now keeps busy doing radio shows and crafting his second novel.

Haldeman, the utter Nixon loyalist, turned on his former boss, by characterizing him in print as being in on the coverup "from day one." but recently, Haldeman made a try at reconciling with Nixon and, before the summer breezes blow again, will probably have made peace with him.

It is Mitchell, 65, Who has remained the same and also probably suffered the most.He and his wife, Martha, separated during the Watergate Ordeal, and she finally died of cancer. He was disbarred in New York and went broke; his debts are estimated at $500,000.He took custody of his daughter, Marty, and arranged for friends to look after her since he's been in prison.

While in prison, he had two major operations-the first, to remove a huge aneurysm on his aorta, which threatened his life; the second, on an arthritic hip, to restore it with a ball-socket prosthesis. During his recovery form the second operation, Mitchell nearly died when he suddenly suffered severe internal bleeding.

Though his friends have been good to him, Mitchell is technically homeless. He moved from his rented New York apartment, gave away most of his furniture and household effects, and will have to accept hospitality when he leaves jail.

His daughter, an honor student in high school, is now a freshman in her first year at Georgetown University, lives in a campus dormitory, and stays with Mitchell's friends on holidays or on special weekends.

Some of Mitchell's friends are angry about the way he was treated by the federal parole commission, charging that he should have been released sooner and that there was political meddling with his case. The commission's chairman, Cecil C. McCall, denies all this and says Mitchell's case was decided on about as open-minded a basis as is humanly possible.

If there is one serious flaw in the commission's handling of Mitchell's case, it is that commission member Dorothy Parker, whose husband was fired at the Justice Department for interfering with a criminal case when Mitchell was attorney general, should have "recused" herself from any judgment on Mitchell the prisoner. She didn't.

Interestingly enough, Attorney General Griffin Bell and Watergate prosecutor Loen Jaworski bothe said publicly that Mitchell had paid for his wrongs and should be released. Jaworksi wrote an unsolicited letter saying that Mitchell-because he was not a federal official when he got involved in Watergate-was less culpable that those who were in government.

But all this is behind Mitchell and the rest of us now. The Bureau of Prisons has granted him a short Christmas leave, and he will spend the time in Washington and New York with his family. Mitchell will be a free man in a few weeks, and his friends will bo doubt give him a private welcome home party. He will probably be as salty as ever and try to brush away such expressions of "hearts and flowers stuff"-as he calls it.

He was the most stoical figure in Watergate, and he's not about to join the Moonies or the born-agains. The way his hip has healed, he might try some golf, though.