Abstract: A method for the determination of 17α-methyltestosterone (MET) in aquatic products by UHPLC-MS/MS was proposed. The sample was extracted with tert-butyl methyl ether, and the extract obtained was purified by gel permeation chromatography and HLB SPE column. Eluate from the column was evaporated to near dryness by N2-blowing at 40 ℃, and the residue was dissolved with the mobile phase mixture. ACQUITY UPLC BEH C18 column was used as chromatographic column, and a mixture of acetonitrile and 0.2% formic acid (40+60) was used as mobile phase in gradient elution; positive electrospray ionization and multiple reactions monitoring mode were used in the detection. Linearity range for MET was kept between 0.50-100 μg·L-1, with lower limit of determination (10S/N) of 0.5 μg·kg-1. Tests for recovery were made at the concentration levels of 1.0, 5.0, 10.0 μg·kg-1 of standard MET, giving values of recovery in the range of 87.0%-94.2%, with RSD′s (n=5) less than 6%.