Abstract: This study aimed to evaluate the effect of 17α-methyltestosterone（MT） on m RNA expression of vtg gene in liver of Brachydanio rerio. The male and female Brachydanio rerio were treated with different concentrations of MT for 7 days, and q RTPCR assay were used to determine the m RNA expression of vtg gene in their livers. For female Brachydanio rerio, the m RNA expression of vtg gene in 25 ng/L MT treatment group was significantly reduced after 7 days（P〈0.05）, and that in 50 and 100 ng/L MT treatment group was extremely significantly reduced（P〈0.01）. For male Brachydanio rerio, there were no significant differences in the m RNA expression of vtg gene between 25 ng/L MT treatment group and control group after 7 days（P〈0.05）.However, the m RNA expression of vtg gene in 50 and 100 ng/L MT treatment groups was significantly and extremely significantly increased（P〈0.05 and P〈0.01）, respectively. The results suggest that the vtg gene in liver of Brachydanio rerio is sensitive to MT,and it is potential to serve as a biomarker for MT monitoring in environment.