Abstract: Sex reversal syndrome is a disorder of sexual differentiation. Karyotype and phenotype are oppositive， including the 46， XX males and 46， XY female. The possible mechanisms include the translocation of Yp?-Xp end， the translocation of chromosome and autosomal， the undetected XX/XY chimeric， over?-expression or deletion of SOX9 gene， and mutation of other genes or molecules involved in sex determination. There are great clinical heterogeneity. Infertility after marriage may be the main cause for a 46， XX male to see doctor. 46， XY female often see a doctor because of primary amenorrhea. Diagnosis should be done as early as possible. Prenatal diagnostic techniques can be used to avoid the birth of those sick children. Therapy for this syndrome includes surgery， drugs and psychological intervention.

Key words: Sexual differentiation, Sex reversal, gonadal, Chromosomes, Sex determination （ｇｅｎｅｔｉｃｓ）