Sens. Paul Laxalt (R-Nev.) and Lowell P. Weicker (R-Conn.) said yesterday they are preparing a lawsuit challenging the new senate thics code, which limits a senator's outside earnings from such things as honoraria and law fees to $8,625 a year starting in 1979.

"We are trying to protect the Senate from its own folly," said Laxalt.

The ethics code was approved early this year over the protests of a number of senators, who argued it was all illegitimate for the Senate to impose a limit on salaries and speaking fees earned by senators by outside work. The code also requires reports of holdings of a senator's wife and children and bars wives from receiving gifts from a number of specified sources, such as foreign lobbyists.

Laxalt said others who may join in the suit are S.I. Hayakawa (R.-Calif.), Barry Goldwater (R-Ariz.), Carl Curtis (R-Neb.), Clifford P. Hansen (R-Wyo.), Malcolm Wallop (R-Wyo.), but that so far only he and Weicker are definite.

Laxalt and some of the others met with Washington attorney Marion Harrison two days ago to discuss the possible suit. Laxalt said he had asked Edmund S. Muskie (D-Maine) who had strongly opposed the $8,625 limit to join the suit but didn't know whether he would.

Laxalt said he hoped to file the suit here in a three-judge federal court, from which it could go directly to the Supreme Court is necessary. The grounds would be that the earnings limit and the requirements on reporting of wives' income and prohibiting certain gifts to wives are unconstitutional. The basis would be that they add qualifications for Senate membership beyond those set forth in the Constitution.

Weicker early yesterday revealed Committee, which is assigned to police the new ethics code.The suit wouldn't be against the whole code, only specified provisions.

Wallop, in an interview, said, "The breadth of the challenge is still under consideration, but the limit (on earnings) is one (aspect) for sure." He said a ban on a senator lobbying his former colleagues for a year after he leaves Congress might also be challenged as unconstitutional.