The Houston Rockets, as expected, signed former Washington Bullet guard Tom Henderson to a three-year contract yesterday. In a surprise move, they also announced the signing of center Moses Malone to a new three-year contract believed to be worth $1 million a year.

In return for Henderson, who reportedly will earn $200,000-a-year on a no-cut pact, the Rockets gave the Bullets a first-round choice in the 1980 draft.

Lee Fentress, Malone's Washington-based attorney. told a Houston press conference, "It is fair to say that Mo's (Malone's) contract makes him the highest-paid pro athlete for a team sport in the world.

"I'd say (tennis player) Bjorn Borg makes $3 million or $4 million counting all of his endorsements, but I know of no team salaried athlete making more than Mo."

Ray Patterson, Rocket general manager, refused to confirm the salary reports. Referring to the claim by Fentress, Patterson said, "Geez, I don't know about that. That's very heavy. I don't know what everyone else in the world is getting."

Malone, voted most valuable player in the National Basketball Association last season, led the league in rebounding with a 17.6 average and ranked fifth in scoring at 24.8 points per game. His 587 offensive rebounds set an NBA record.

"If (Fentress) said it, then I guess it's true," said Malone, who had talked earlier in the year about playing out his option in Houston, and possibly signing with the Bullets.

Today, however, Malone said he never intended to become a free agent at the end of the season.

Asked how it felt to be possibly the richest salaried athlete, Malone said, "I think I wasn't doing too bad before I signed . . . I'm happy with the new contract."

Henderson, who earned $165,000 as a Bullet, decided against signing a new contract with Washington last year, a disappointing season for the former Olympian and University of Hawaii star who made only 33 percent of his shots.

To replace the play-making Henderson, the Bullets last week signed free agent Kevin Porter, sending the Detroit Pistons first-round choices in 1980 and 1982.

"(Henderson) has been a good quarterback as far as running a good ball club is concerned," Patterson said. "We never had one person who could take over the club. John Lucas did it sometimes (in the 1977-78 season), but I'd get up in the morning and never know who was running the club . . .

"Tom's the kind of guy who can. He's a good team player and the sum total is greater than the individual."

Del Harris, the Rocket coach, said he would not put pressure on Henderson to score.

"We'd like for Tom to be a medium threat to score," Harris said. "We'd like people to guard him."

Bob Ferry, the Bullet general manager, said Henderson "Will fit in (with the Rockets) just like he did here. He gets the ball up the court to the right person at the right time. He's a team-oriented player who has the ability to make other people around him better."

"My role with this team is different from (Calvin) Murphy or (Mike) Newlin, so I'm not worried," said Henderson, 27, who averaged 10.6 points and six assists last year.

Henderson's signing gives the Rockets six guards with guaranteed contracts. Patterson said the Rockets have until Oct. 13 "to take care of the problem."

"Other clubs are interested in some of our players," Patterson said, "and we'll probably get down to four or five (guards)." CAPTION: Picture, Tom Henderson