Sophia Loren has finally come home. But rather than heading for the magnificent baroque villa she and her husband, producer Carlo Ponti, once owned at Marino in this city's Alban Hills, her destination was far less glorious: the women's jail in Caserta, outside her home town of Naples, where she is supposed to serve a 30-day term for an old tax evasion charge.

Two years ago when the sentence was confirmed, the glamorous, dark-haired film actress had said that once certain work commitments had been fulfilled she would return to "do my duty and submit to the decision of the judges of my country." But few had taken her seriously.

Today, however, the 47-year-old Italian actress, best known for such movie roles as "The Gold of Naples," "The Pride and the Passion," "Desire Under the Elms," "Two Women" (for which she won an Oscar), "Marriage, Italian Style" and "The Countess of Hong Kong," arrived with her sister, Maria Scicolone, at Rome's Leonardo da Vinci Airport, where she was met by a crowd of reporters and photographers--and by the Italian police, who boarded the plane to meet her and provided a white Alfa Romeo.

Wearing huge brown-tinted sunglasses, an olive green-and-red silk dress with a gold vest and carrying a bouquet of daisies, Loren appeared resigned but somewhat bitter. "I am not a crook," she told reporters, adding she was determined to serve what she termed "an unjust sentence," not because--as some said--she is soon to make a TV film for director Lina Wertmuller but "because I love Italy and because I want to be able to see my mother, my sister, my country and my roots."

Loren said the tax tangle in which she'd become involved--failure to pay the equivalent of $180,000 in supplementary income taxes connected with her 1963 return--was not her fault but that of an accountant who has since died. "I am worried, very worried about this month that awaits me in jail," she said. Although a request to Italian President Sandro Pertini for a pardon has so far gone unanswered, she insisted that "I have faith in the judicial system of my country." Then, after being formally advised of the incarceration order against her, she was driven by police from the airport toward the waiting prison cell.

The Associated Press reports that fans and fellow inmates cheered Loren as she was ushered to her 15-foot-square private cell, which has a bed, television set and bathroom. It is, they added, painted pink, has an unbarred window and looks out over an enclosed courtyard. The inmates are permitted to wear their own clothes. The prison has 10 cells and is run by six nuns. There are 26 prisoners in the jail serving sentences for crimes ranging from prostitution to homicide.

Reactions to the news of Loren's arrest and jail sentence were mixed. "Its a terrible shame," said an elderly woman who shook her head, complaining that most of Italy's tax evaders get away with their crimes.

But a wave of irrepressible Roman cynicism led others to conclude that it was a publicity stunt and, in any event, that the actress was sure to find herself in a luxury cell, with flowers, wall-to-wall carpeting and all the other trimmings. "I bet she won't be in there for over 24 hours," said a waiter. Prison officials have said, however, that Loren will be treated like anyone else. There was some speculation that the semi-liberty formula that has been used with other celebrities may be extended to the world-famous actress. In this case, Loren would have to spend nights in the prison, but would be allowed out during the day.

Loren and Ponti, who have been French citizens since their marriage, left Italy in the early 1970s, largely because, they said, an escalation of kidnapings made them fear for their two children's safety. However, not long after, they ran into trouble with Italy's financial authorities, who accused them of illegally exporting capital.

In 1979, Ponti was sentenced, in absentia, to four years imprisonment and a heavy fine, which the authorities collected by placing a lien on real estate and other property here. Loren was acquitted on this and another charge that she had tried to smuggle valuable art works abroad. The income tax issue, for which she must also pay a fine of $9,300, is an entirely separate issue.

Loren has not been in Italy since July 1980. That occasion was not a particularly pleasant one, either, since during it she and her sister were robbed and maltreated by a man who approached their car, which had been pulled over to the side of a highway because it had a flat tire.

However, this does not seem to have dulled her appreciation for Italy. Before boarding an Alitalia flight for Rome in Geneva this morning, Loren said she was making the trip because "I want to be able to smile again, and I need the Italian sun." Picture, Sophia Loren, UPI