The Senate, rejecting a major challenge to its proposed new ethics code, voted yesterday to include an $8,625 annual ceiling on a senstor's outside earnings from speeches and articles.

On a roll-call of 62 to 35, the Senate killed an amendment by Edmund S. Muskie (D-Maine) to strip out the $8,625 ceiling and leave in effect an existing $25,000 lid that was adopted two years ago.

The limit in the new code does not apply to dividend and interest income - just to "earned" income such as that from speeches, articles and TV appearances.

"There is every indication the Senate is panicking and will vote for anything in the name of ethics," said Muskie, declaring he may have to sell one of his houses in order to raise money if he can't supplement his $57,000 annual salary from lecture tour eearnings above the $8,625 lid. In the three years from 1973 through 1975, Muskie earned a total of about $77,000 in honoraria.

Muskie said Sen. Gaylord Nelson (D-Wis.), who headed the special ethics committee that wrote the proposed code," is putting a cap on my income and he doesn't give a damn on what the consequences may be for me and my family."

Nelson angrily retorted, "The senator from Maine voted against the pay increase and then he comes here shedding hot tears flooding the place."

The reduction of the honorarium ceiling from $25,000 to $8,625 was proposed by the Nelson unit after congressional pay was raised from $44,600 a year to $57,500 on March 1. The House has already adopted a similar ceiling for its members.

Supporters of the lower limit, which is 15 per cent of a congressman's annual salary, say it is unseemly and embarrassing for the public to see members running around collecting fat lecture fees when they have just had a substantial pay increases. In some past years, before there were any limits, senators have earned in the $40,000 to $50,000 range from speaking, and one, Hubert H. Humphrey (D-Minn.), earned $83,451 in 1971.

Muskie argued that the new limit is unfair because it applies only to "earned" income such as honoraria from speeches, articles and TV appearances, but doesn't apply to "unearned" income from dividends, interest or rents collected by senators.

Muskie said this means senators with family wealth for business holdings can supplement their Senate salaries by tens of thousands of dollars merely by sitting home clipping coupons, while poorer senators who can earn extra money only from the lecture circuit are limited to $8,625.

However, proponents of the limitation said there isn't much the Senate can do if a man is born rich and it may well be unconstitutional to deprive him of the proceeds of his own property.

They said it in't the purpose of the new code to equalize wealth among senators, but only to make sure that a senator doesn't take advantage of his public fame and office to make large amounts of money performing personal services that require time, effort, absence from the Senate and invote conflicts of interest.

Before defeating Muskie's amendment to lift the $9,625 limit althogether, the Senate turned back another Muskie amendment to leave it in effect for speeches but also apply it to interest and dividends.

Under this proposal, any interest and dividends in excess of the limit would have been set aside in a trust for a senator until he left office. This amendment was beaten, 67 to 29.

Debate on other portions of the code continues today.

Majority Leader Robert C. Byrd (D-WVa.), convinced the Senate's prestige would plunge if an honorarium limit weren't imposed once Congress had received a pay raise, put his influence on the line to defeat the Muskie amendments. Byrd worked strenuously behind the scenes, aided by Assistant Leader Alan Cranston (D-Calif.), to round up votes against the Muskie proposals.

Muskie said he has always lectured to make extra money because he considers it a clean and honorable way to supplement income. On Monday he told reporters that "It is conceivable that I may not be able to finish out by term" because of financial pressures if the $8,625 limit were upheld. "I'll try to live with it," he said glumly.