A transsexual who accused the U.S. Postal Service of discrimination because it refused to let her take a job won a preliminary victory here yesterday in federal court.

U.S. District Judge John H. Pratt rejected motions to dismiss the case and said it would go to trial on claims that the Postal Service violated her constitutional rights to equal protection and due process. Pratt said the plaintiff, identified only as Jane Doe, also could have her case tried as handicap discrimination under the federal Rehabilitation Act, which says a qualified person cannot be denied a job solely because of a handicap.

Citing previous court decisions, Pratt threw out Jane Doe's claims that transsexuals were covered by federal sex discrimination laws and constitutional rights to privacy, but her attorney, Victor M. Glasberg, said clearing the way for trial on the two other claims was a significant step forward in her case.

According to court papers, postal officials offered the woman a temporary job as a typist while she was still a male, but then withdrew it when she told them she planned to undergo a sex change operation and wanted to dress as a female for six months beforehand. The postal officials said the sex change would be "disruptive" in the office.

The suit says the postal service refused to reinstate the appointment even after the plaintiff offered to remain a male and dress as a male for the six-month term of the job. Glasberg said Jane Doe underwent the sex change operation in November 1983. He said that since then, as a female, she has been working as a secretary for another government agency.