Elizabeth Taylor sat propped on a pillow the other day in a pink-peony-laden $1,800-a-day suite at the Plaza Athenee, one of her magni-carat diamond rings saddled prominently to a left knuckle, two private secretaries within earshot and a pack of menthol cigarettes poised on her lap.
What Miss Taylor, who was in New York to be honored by the Film Society of Lincoln Center, wanted to talk about most was her weight.
''I'm a size 6,'' the 53-year-old actress boasted in an interview. She looked girlishly trim in a low-cut buttoned white sweater that she wore over tight-fitting jeans. Her black-and-gray-peppered hair was puffed in the shape of a helmet and her eyes heavily made up Cleopatra style with shadow.
The interview, which lasted an hour, touched on a range of topics, including Miss Taylor's fund-raising efforts for AIDS, her ''thrill'' at being honored by the Film Society of Lincoln Center (she purchased not one but two new dresses for the occasion so that at the last moment she could choose), a new television picture she will soon start rehearsals for with Robert Wagner and her prospects for marriage (there are none at present but ''I'm an eternal optimist'').
She said that she hates watching herself on television and in the movies.
''I hate to see myself on the screen,'' said Miss Taylor, who started her M-G-M film career as a companion to Lassie in 1943, won Academy Awards as a trollop in ''Butterfield 8'' in 1960 and a shrew in ''Who's Afraid of Virginia Woolf'' in 1966. ''I hate the way I look. I hate the sound of my voice.''
Still, it was diet and her efforts at weight control that seemed foremost in Miss Taylor's mind.
''I lost the 25 pounds I gained,'' said Miss Taylor, volunteering that she had first lost 50 pounds but then regained 25 when she injured her back last year in a fall while dancing and had to be confined to bed. Having oral surgery didn't help either, she said, because ''I stuffed myself with ice cream and malteds. I was angry, bedridden, limiting my life to zilch. I started indulging. I could see myself blow up and I finally said 'No.' It's ridiculous. I had a long chat with myself in the mirror.'' Plans a Diet Book
Miss Taylor said she put herself on yet another diet - her own - and was so successful, she said, she now plans to write a book about it. The diet essentially stresses fruits and vegetables, no red meat and plenty of fish, but includes such palate pleasers as chicken barbecued with lime and potato skins. However, the key, she said, is not just losing the weight but keeping it off, a challenge that ultimately boils down, Miss Taylor says, to ''self-esteem.''
''You have to try to get your head at the right place,'' Miss Taylor said. ''Where you can make it click. Without that inner click it doesn't matter how many fad diets you go on.''
Miss Taylor said she now keeps her weight down by eating carefully but always allowing herself one day a week to ''pig out.''
She elaborated: ''Fried chicken. Mashed potatoes. With lots of gravy. Lima beans. Corn. Chocolate cake of some kind. But then the next two days you really have to watch it.''
She added, ''It's not like alcohol. Life on a total diet for the rest of one's life would be totally depressing.''
Every day, Miss Taylor said, she steps on the scale and tries to keep her weight between 123 and 125 pounds.
''Last year I got down to 119 but it was too low,'' Miss Taylor added decisively. ''It looks great with clothes on. But not,'' she said hesitating for emphasis, ''clothes off.'' Recalling Mike Todd
Miss Taylor, spoke with candor about her ''hang-ups'' and vulnerabilities. She recalled the death of her third husband, Mike Todd, when she said their daughter, Liza, 28, was expecting her first child soon.
''She was only 6 months old when Mike died,'' Miss Taylor said wistfully.
Suddenly one of Miss Taylor's secretaries rushed into the room, and mumbling the name of the caller, said she should come to the telephone.
''There's a race horse called Elizabeth Taylor,'' Miss Taylor said to a visitor, as if to explain why she had to take the call.
But she had misunderstood. The call was not from the woman who owns the race horse named after the actress but rather from her son-in-law. He was calling to to announce that her daughter, Liza, was in labor.
''I'm supposed to go to the theater tonight,'' Miss Taylor said, returning from the telephone with tears in her eyes and visibly shaken. ''How am I ever going to sit through it?''
Her sixth grandchild was a boy.