Abstract: Objective To study the relationship between the change of sex hormone and reproductive dysfunction caused by obesity in mice.Methods High-fatdiet was given to 96 mice for 8 and 19 weeks.Blood samples were collected and testis,epididymis,and seminal vesicles were took out and weighed at the end of treatment.Sexhorm one levels were detected with enzyme-linked mimunosorbertassay(ELISA).Results The weights of testis(0.62±0.08 g/10g) and epididymis(0.25±0.05 g/100g) of the diet-induced obese (DIO) mice were significan tly lower than those of the control (0.75±0.07 g/100 g,0.30±0.02 g/100g) after the treamtent of 19 weeks.Spermactivity of the DIO mice (31.37±13.86%) was significantly lower than that of the control(49.76±21.71%).After treatment of 8 weeks,the level of gonadotropin-releasing homone(GnRH) of the DIO mice(17.82±1.98 mIU/mL) was lower than that of the control(33.46±4.54 mU/m L) (P < 0.05).However,the level of GnRH of the DIO mice(48.74±8.95 mIU/mL) was higher than that of the control(27.12±4.54 mIU/mL) (P < 0.05) at the end of the treatment of 19 weeks.Conclusion Obesity may affect the development of reproductive organs and affect sperm quality in mice.There is maybe are lationship between the change of sex hormone and reproductive dysfunction caused by obesity.