SRY（sex-determining region of the Y chromosome） gene plays a key role in sex determination in the mammal and some evidences suggest that SRY encodes the TDF （testis determining factor） that is required for male sex determination. Sox genes are closely related to the SRY and code for proteins with a characteristic DNA-binding motif known as SRY-type HMG （high mobility group） box. A large number of Sox genes have been found in a wide variety of species throughout the animal kingdom, from human to Drosophila. Penaeths monodom is an important economical species and its heteromorphic sex chromosomes have not been found. So far, little information is known about P. monodom＇s molecular genetics of sex determination. In this paper, the technique of PCR is used to amplify the Sox genes of P. mondom with a pair of primers which specially amplify the conservation sequences of man HMG-box gene. In addition, the technique of SSCP（single strand conformation polymorphism） is used to analyze the amplification products. The results of PCR and SSCP analysis suggest： 1 ）The lengths of the fragments of PCR products are about 350 bp and 220 bp in both female and male shrimps. 2）There are Sox genes in these shrimps. 3） Introns are also found in Sox genes which is 350 bp. 4） There are different Sox genes in female and male shrimps. And the sex-determining mechanism of prawn is also discussed.