Abstract: OBJECTIVE To develop a UPLC-MS/MS method to determine illegal chemical composition added into the slimming health food. METHODS The analysis was performed by a UPLC-MS/MS system with Eclipse Plus C₁₈(2.1 mm×50 mm, 1.8 μm) column, with 0.02 mol·L^-1 acetic acid (A)-methanol (B) as mobile phase by gradient elution at a flow rate of 0.3 mL·min^-1, and the column temperature was 40℃. Multiple-reaction monitoring (MRM) was performed to identify and quantify 8 chemical drugs, including ephedrine hydrochloride, caffeine, furosemide, fenfluramine, phenolphthalein, N-single demethylated sibutramine, N,N-didesmethylsibutramine and sibutramine. RESULTS A good resolution of 8 kinds of chemical drugs were obtained under this UPLC-MS/MS condition. Eight linear calibration curves were obtained with R² ≥ 0.996 7. The limits of qualitation and quantitation were in the range of 0.042-0.175 μg·mL^-1 and 0.126-0.525 μg·mL^-1. The precision of the method were showed by RSD (n=6) ranged from 1.7% to 4.7%. The average recoveries (n=6) were in the range of 90.3% to 105.1% at three concentrations levels. CONCLUSION The method is simple, accurate, and highly sensitive, which can be used for the determination of illegally added chemical drugs in slimming health foods.