The cDNA-SRAP technique was applied to analyze the difference of gene expression in the mucus between female and male ricefield eel and to screen sex-related molecular markers.Twelve polymorphic markers selected from 64 pairs of primer were used for cDNA-SRAP amplification and 123 polymorphic loci and 4 sex-special fragments were obtained.After gel extraction,cloning and sequencing,4 sex-special sequences were obtained and submitted to db GSS (data of genome sequence survey).The result of blast analysis showed that only one sequence hit the Lipotes vexillifer sulfate/thiosulfate import ATP-binding protein CysA-like,which was used to design one pair of primer for semi-quantitative RT-PCR.PCR product was amplified in mucus of both female and male ricefield eel.However,there was a significant difference in their expression levels,with the expression in male significantly higher than in female,which may due to the difference of skin cells and mucous gland cells between female and male.