Abstract: The present paper concerns the variance of the sexual hormone in blood of three kinds of TESTUDOFORMES in different periods.The conclusions may be summarized as follows:1.With regard to the three kinds of male animals,the amount of sexual hormone in blood plasma of Clemmys mutica is the highest (304.46±292.15 ng/dl),whereas Trionyx sinensis Wiegmann is the lowest (122.31±64.44 ng/dl).2.With regard to female animals,the amount of sexual hormone in blood plasma of Trionyx sinensis Wiegmann is the highest (75.93±67.35 pg/ml),whereas Chinemys reevesii is the lowest (50.16±35.75 pg/ml).3.Since the amount of testosterone in blood of male animals in the mating period is larger than that of in the non-mating period,it is suggested that the testosterone is related to the formation of sperms.4.The amount of estradiol in female ones is always changed with the development of ovarion cycle.