In order to explore the function and molecular mechanism of sex-lethal gene in Procambarus clarkii,four Sxl cDNA sequences from P. clarkii were obtained using rapid amplification of cDNA ends,and their expression in different tissues and at early developmental stages were detected by quantitative fluorescence PCR. Bioinformatics analyses revealed that PcSxlβ and PcSxlδ were 77 bp longer than PcSxlγ,and the predicted amino acid sequence of PcSxlβ and PcSxlδ were shorter than that of PcSxlγ. The PcSxl sequences was highly similar to that of Cherax quadricarinatus (75.76%). The analysis of conservative domain showed that all the predicted amino acid sequences of the four transcriptional isomers had two highly conservative RRM domains. The expression analyses showed that PcSxl was highly expressed in the antennal glands and gills of adult males,and in the midgut and foregut of adult females,and was significantly higher in the female ovaries than the male testis. During the early developmental period of the crayfish,the expression of the genes was the highest at the nauplius stage,but decreased at the zoea stage; however,the expression level increased at the first day after hatching,and then showed a gradually decreasing trend. The results of this study suggested that PcSx was involved in sexual differentiation in P. clarki.