A federal judge yesterday reduced a former Washington restaurateur's drug smuggling sentence by six months after his lawyer said the man's business had been ruined and his life threatened following his conviction for helping to import $32 million of heroin.

District Judge Albert V. Bryan Jr. told Mohammed (Mike) Roshan, 35, former operator of The Golden Table Restaurant in Washington, he will have to serve 18 months in jail, rather than the two years the judge had imposed in 1980. Roshan, who was injured last weekend during a fight in a Tysons Corner restaurant, is scheduled to begin serving the sentence July 24.

Roshan's lawyer, Alan H. Levine, argued yesterday that Rosan had already suffered considerably from his conviction. He said Roshan's fight last weekend was with a man Levine claimed was linked to the Drug Enforcement Administration. Levine also complained that a Washington Post story on a restaurant venture of Roshan's had forced his client to sell the business.

Levine told Bryan that he believed the DEA was the source for the story and that Roshan's alleged assailant is involved with the DEA. Asked about the charge after the hearing, Levine declined to elaborate.

DEA officials have refused to discuss the incident.

Roshan was stabbed at least three times at a Tysons Corner restaurant in a scuffle with a man Fairfax County police have identified as Mike Burke, also an Iranian national. Roshan was released from Fairfax Hospital yesterday morning and he appeared in court with severe facial lacerations and his right arm in a sling.

Burke was charged with malicious wounding with intent to maim in the incident. A preliminary hearing on the charge is set for July 21, in Fairfax General District Court.

Roshan was convicted on one count of distributing one-half pound of heroin in what federal officers have said was one of the largest heroin arrests in Washington. The other Iranian nationals were also found guilty in the case. w