Last July, when expatriate Czech Martina Navratilova won the Wimbledon tennis championship, she said one thing made her dream-come-true incomplete.

"I don't know if I should cry or scream or laugh," she said at the time, choking back sobs. "I feel very happy that I won, and at the same time I'm very sad that I can't share this with my family."

This afternoon, when strode proudly onto the sunlit Centre Court of the All England Lawn Tennis and Croquet Club to begin defense of the most-prized title in tennis, Navratilova's heart was soaring, her dream more nearly fulfilled.

In the competitors' guest box, hands clasped nervously in her lap, sat her mother, whom Martina had not seen in nearly four years until late Monday afternoon.

"Winning here last year was the greatest moment in my career, but yesterday was one of the greatest moments in my life," Navratilova said after her 4-6, 6-2, 6-1 first-round victory over qualifier Tanya Harford, a sporting moment that transcended everyday fun and games.

Jana Navratilova, a handsome woman of 47, arrived here from Prague Monday and was reunited with her celebrated daughter for the first time since August 1975, two weeks before Martina defected and asked for political asylum in the United States during the U.S. Open championships.

Mrs. Navratilova's two-week tourist visa was granted last Friday, apparently with the personal approval of the Czechoslovakian prime minister, Dr. Lubomir Strougal.

"It went that high," Martina said today, explaining that the invitation she had requested from Air Chief Marshal Sir Brian Burnett, chairman of the All England club, had been forwarded to the prime minister by the father.

"I sent my mother an invitation myself a couple of months ago, but that didn't go through. They refused it . . . then my father got the idea of an official invitation from the All England club. He thought that might work better, and it did," Navratilova said.

"First, they (the club) just sent a telegram, which didn't work. So then I called again and they sent a letter. That finally did it. My dad took it to the prime minister and did a lot of running (around) himself, and it finally went through."

Fifty weeks ago, when the duchess of Kent presented the gleaming gold champion's plate to Navratilova after her thrilling 2-6, 6-4, 7-5 triump over Chris Evert, she offered Martina her assistance in the long bureaucratic battle to get her parents visas to leave Czechoslovakia.

News of Navratilova' victory last year was downplayed, virtually muffled in the government-controlled media of Czechoslovakia. But her mother, father Miroslav and younger sister Jana, who just turned 16, were able to see it by driving to the town of Pilsen, near the German border, and watching a West German telecast.

However, their repeated efforts to obtain either tourist visas to visit Martina abroad, or permanent visas so that they could join her in her adopted hometown of Dallas, have been denied.

"I am very successful now, but I will never be completely happy until I am with my family again," Navratilova said last January, during a tournament in Washington, D.C.

A breakthrough of sorts came in March when Navratilova's 84-year-old grandmother, Andela Subertova, was granted a visa and spent a month in the United States, visiting Martina in Dallas and accompanying her to the Avon Championships in New York, which she won to climax an outstanding winter season.

Then last Friday, word came that her mother would be permitted to join her in England. Martina - who has applied for U.S. citizenship and will be eligible for it in October 1980 - got the news when she phoned her sister in Revnice, the Prague suburb where she grew up.

"When my sister told me, I started crying. And when my mother found out, she was crying. It was very emotional, obviously," Navratilova said today. "I was like a little kid. . .

"After this, hopefully the whole family will get to go permanently. They've asked for a permanent visa, which is the legal way of leaving Czechoslovakia for good."

That would make her dream complete.

Navratilova sensibly kept tight-lipped about her mother's impending arrival to insure that their airport reunion would be a personal affair, away from the glare of the massive publicity that inevitably followed today.

Martina went to Heathrow Airport alone to meet her mother, who was due in at 4:10 Monday afternoon. "I was nervous, very nervous," she said. "The plane was late, naturally. It took another half-hour for her to get through customs, so I didn't see her until quarter after five."

Those few minutes seemed interminable.

"I was just waiting there. When she first came out, I didn't even recognize her. I was just flabbergasted because she looked so good. But she recognized me right away."

And mother brought a present: "Cookies . . . she brought me cookies that she had baked in the morning, before she came over," Martina said.

Monday evening, mother and daughter went to dinner at a King's Road bistro frequented by tennis players during Wimbledon.

Today, the mother-and-child reunion became a matter of public record.

Mrs. Navratilova sat with hands folded atop her pocketbook on the lap of her gray checked pantsuit as her duahgter walked onto the Centre Court, amid ringing applause, and curtsied to the royal box where the duchess of Kent again sat beaming.

Since there are only 96 players in the women's singles draw at Wimbledon, compared with 128 in the men's singles, Navratilova was entitled to a first-round bye. But she chose to play so that she could savor the final thrill of her year's reign as champion: the honor of playing the opening match of Wimbledon's traditional "Ladies Day" in the Elizabethan-style Centre Court.

Navratilova almost got more than she bargained for in Harford, a plucky, athletic 20-year-old South African who played her way into the tournament by winning three qualifying rounds last week.

Harford is a bright and bubbly young lady who sometimes scribbles notes on a clipboard at change games. She once wanted to be a veterinarian, and has set a timetable for herself to dramatically improve her world ranking (currently 135) by the end of the year "or go do something else with my life."

Quick, nimble and self-assured at the net, she started quickly today, read Navratilova's passing-shot attempts perfectly, and cracked some scintillating service returns and volleys in taking the first set.

Navratilova, who eventually settled down and won convincingly as Harford's storm of early winners blew itself out, admitted that having her mother watching was both an inspiration and a distraction, but she didn't use that as a copout for losing the first set.

"That didn't have anything to do with it. I was just kind of in a daze, being out there. I wasn't quite ready for the Centre Court. She played well, and it took me awhile to get going, but once I did I was all right. It was just a matter of breaking her serve for the first time, and then I knew I'd be okay. . .

"My mother told me later she was afraid that she had distracted me, got me so emotional that I wouldn't win. But then she calmed down when I started winning."

Navratilova's thumping serves and volleys, her buzzing passing shots and whistling returns of Harford's increasingly short second serves, gradually took control of the match, and then came the tough part. Afterward, mother and daughter were dogged step for step by reporters and cameramen.

"I'm very happy now . . . I'm very happy now," Mrs. Navratilova kept saying, smiling and waving as a reporters fired questions she had trouble understanding. She seemed a bit bewildered by the media mob scene, but Martina - who is used to it - took her under her wing and guided her through a joint press conference.

"How has Martina changed since you last saw her through a joint press conference.

"How has Martina changed since you last saw her?" Mrs. Navratilova was asked.

She broke into a smile and looked over to her daughter fondly, her eyes seemingly bigger than her silver-rimmed glasses: "Oh, I think she is very pretty now," she said.

"Any other changes?" she was asked.

Another irresistible glance and smile at the trimmed-down, matured Martina. "Oh, yes she was . . ." her voice trailed off and she frowned as she spread her hands apart in a gesture that said "wide as a house."

Once again, the wonderful smile of a prideful mother, and four words of impeccable English, "Now she is skinnier." CAPTION: Picture, Martina Navratilova, right, and her mother Jana enjoy their long-awaited reunion. AP