Moses Malone, a 6-foot-10 center for the Houston Rockets, yesterday signed a $13.2 million offer sheet, worth about $2.2 million a season for six years, with the Philadelphia 76ers that would make him the highest-paid salaried athlete for one season in the country.

Malone, 28, was the most valuable player in the National Basketball Association last season after averaging 31.1 points, second behind San Antonio's George Gervin, and 14.7 rebounds, best in the NBA. The $2.2 million salary offer surpasses the $2 million single-season salary paid to outfielder George Foster of the New York Mets.

The largest long-term contract in team sports was signed two years ago by Magic Johnson of the Los Angeles Lakers. Starting in 1984, he will be paid $1 million a year for 25 years. Foster came to the Mets as a free agent from Cincinnati this season.

Kareem Abdul-Jabbar of the Lakers, Otis Birdsong of the New Jersey Nets and Julius Erving of the 76ers all earn approximately $1 million a year. Boxers such as Sugar Ray Leonard and Larry Holmes, tennis players such as John McEnroe and Ivan Lendl, and some jockeys earn huge sums of money, but little of it is earned from salary.

The Rockets, for whom Malone has played the past six seasons, will have 15 days from the time they receive a copy of the contract to match the 76ers' terms. If the Rockets match Philadelphia's offer, Malone, under terms of the NBA contract, must remain in Houston.

Philadelphia traded its center, Darryl Dawkins, to the New Jersey Nets last week for a No. 1 draft choice in 1983.

Houston General Manager Ray Patterson said he would have to study the offer sheet before deciding whether the Rockets would match it.

The 76ers refused to disclose the terms of the contract, but radio station WSSV in Petersburg, Va., Malone's hometown, reported yesterday morning it was told by Malone that he will be paid about $2.2 million a year.

Malone left for Amsterdam yesterday to begin a seven-game European tour with other NBA players and was not available for comment. The trip will continue to West Germany, Italy and Spain. Malone is not due back until Sept 13.

By that time, he may know whether to pack his bags for Houston or Philadelphia. League general managers contacted yesterday by The Washington Post were guessing Houston.

"The bottom line is that this will cost Houston more money," Jerry Colangelo of Phoenix said. "I think it would be difficult for him to play anywhere else."

Don Nelson of Milwaukee agreed, saying that Houston's fan support is based heavily on Malone's presence and that the Rockets already have committed themselves to keeping the all-star center.

"I would think that Houston would have to go the extra mile now," the Bullets' Bob Ferry said. "It all depends on how the contract is drawn up. How much money is up front and how it will be distributed.

"This may eventually be a great thing for Philly -- although they've got to win it all or they're right back where they started -- but it's not good for the league," Ferry continued. "We've got to keep things in perspective."

Charlie Thomas, a car dealer in Houston who recently took control of the Rockets from Gavin Maloof, said that Houston's last offer was about $9.5 million ($1.9 for five years) and that he still wanted to sign Malone.

"When I sit down and start to think what the difference is in real money (with deferred payments), I don't think we're that far off in our offer," Thomas said. "I would not rule out paying $13 million to keep him, but first we'd have to see how it would affect ticket prices."

The Rockets set a team attendance record last season, when they finished tied for second in the Midwest Division with a 46-36 record.

Patterson said the Rockets have three options: to match the offer and sign Malone, to match the offer and trade him or to work out a deal with Philadelphia.

"Who knows what we'll do?" the general manager said. "I really don't know what is in the contract. It could have all kinds of deferred stuff and accelerated payments. You really need to get the offer sheet and relate it to your cash flow."

Coach Billy Cunningham said the 76ers made the deal because they felt they needed more rebounding and physical play to win the championship. Philadelphia beat Boston to win the Eastern Conference title, but lost the championship series, 4-2, to Los Angeles.

"He (Malone) has the ability to make everybody on our team a better player," Cunningham said. "I think he can give us 12 rebounds a game. His presence will make Julius (Erving) more effective on the break."

Malone agreed to attend the University of Maryland in 1974, then signed instead with Utah of the American Basketball Association. When the league folded, he was selected by Portland in a special draft, then traded to Buffalo for a first-round draft choice. After six games, he was dealt to Houston for two first-round picks and averaged nearly 24 points and 15 rebounds in his six seasons with the Rockets. CAPTION: Picture, 76ers offer would pay Malone, center, $2.2 million annually. UPI