Xiao An used to primp before the mirror for hours, but a dab of rouge and the permanent wave never turned a plain girl into a beauty.

So she marched down to the office of Dr. Fu Longyu and, for the equivalent of $20, walked out with a new pair of eyelids adorned with a Western-style fold.

After the stitches were removed and the swelling went down, Xiao An joined the growing number of Chinese women who have endured a painful operation to modify the most distinctive feature of the Chinese face--the creaseless eyelid.

Many Chinese women, who for years fashioned their own brand of the feminine mystique wrapped in baggy trousers and Mao caps, now believe the classic Asian eyelid makes their eyes look too squinty.

"Sometimes I could make my eyelids fold naturally by pressing the skin together," said Xiao An, 20, a chemical factory worker. "Then I'd run to the mirror and admire my eyes. They looked so elegant."

Although such decadent thoughts could have qualified for a public beating a few years ago, today they lead dozens of Peking women each month to the modest quarters of Fu Longyu, a plastic surgeon who uses his bed for a makeshift operating table and performs the delicate surgery under a reading lamp.

"A few years ago, ideological purity was the only requisite," Fu said recently between operations. "Now people pay as much attention to outside beauty as inside beauty."

Although most of his patients are in their twenties, women of every age, occupation and motivation wander into Fu's clinic on the long, winding Suzhou Alley.

In the past year, he has operated on lonely hearts hoping to land a beau and aspiring actresses hoping to land a role. There have been middle-aged women trying to resist the ravages of time and teen-agers casting about for a self-concept.

Fu, a frail man of 58 with a blind left eye, offers two surgicial procedures: the small fold for patients who want to maintain an Oriental identity, and the deep fold for women who want eyes as big as Debbie Reynolds'.

"The cadres who come here always get the small fold," said Fu. "They don't dare to look too Western. But some young ones who want to become movie stars ask for the Western style."

Patients who cram into Fu's one-room clinic every morning deny they are succumbing to Western influence, claiming they merely hope to make their eyes "harmonious" with their face, not Occidental.

"When I was young, my eyes went quite well with my face," explained a 42-year-old drama teacher. "As I've aged, my eyes have gotten smaller. They've lost harmony with my face. This is when a plastic surgeon can help."

Although many chauvinistic Chinese believe their ancestors invented beauty along with gunpowder, the popular standard for female sublimity has undeniably been influenced by the recent opening to the West.

Padded bras are becoming common apparel among the urban young, and a national sports magazine acknowledging the woes of being flat-chested suggested exercises and plastic surgery as a cure.

Chinese matrons wait in long lines for octopus-like hair-curling devices that are making big waves in most cities.

Despite the few obvious rub-offs from the West, changes come slowly to a society where bound feet were the rage less than 40 years ago. During the Cultural Revolution of the 1960s and 70s, radical chic was Army fatigues for both men and women.

Communist leaders today try to monitor fashion with regular denunciations of "weird and immoral" hair styles and garb from the West, but they seem willing for the time being to avoid tinkering with evolving concepts of physical beauty.

It was with an eye to beauty that Dr. Fu nailed up a copper sign outside his little house 14 months ago and started taking patients after obtaining local government approval to operate as the only private plastic surgeon in Peking.

He learned the skill as a young medical student more than 30 years ago, and after decades of virtual inactivity he revived the technique of slicing out a layer of fatty tissue from underneath the eyelid so that the outer skin folds loosely over the eyeball.

Every morning Dr. Fu dons his white surgical gown, cap and mask and goes to work in his cluttered, unheated operating room while as many as five patients wait their turn. He sterilizes his instruments himself and keeps them on a tray placed atop his dresser along with a supply of local anesthetic.

Fu said about 600 women and a few men have had the surgery since he opened shop, and he has turned away thousands more because of his poor health. He sees each patient twice during the seven-day recovery period to make sure they remain free of infection.

State hospitals also perform the operation, although the waiting list is said to be very long. The hospitals give special priority to the politically influential, require complicated approvals from work units and charge higher fees than Fu.

At the clinic recently, two women of varying background and age who are both proud new owners of creased eyelids gave similar justifications that may say more about the univeral role of beauty than its place in China.

"I'm no match for my handsome boyfriend," said Xiao An, the chemical worker who once fantasized about folded lids. "I wanted to catch up to him."

"My husband has been very considerate," said the drama teacher. "I want to show him I love life. Life is beautiful, so people also should be."