Objective]To establish a rapid resolution liquid chromatography-mass spectrometry(RRLC-MS) method for sibutramine hydrochloride, ephedrine hydrochloride and furosemide, which is the illegally added substances in diet pills. [Method]The chromatographic conditions: Agilent SB-C18 column(2.1mm×50mm, 5μm). The mobile phase consists of acetonitrile(containing 0.1% formic acid) and 0.1% formic acid solution, gradient elution with flow rate of 0.2mL·min-1; The MS conditions: electrospray ionization(ESI) source, with positive and negative ions, multiple reaction monitoring(MRM) mode to detect contents of prohibited substances in diet pills. [Result]Under the above conditions, all seven diet pills were detected with the sibutramine hydrochloride and ephedrine hydrochloride. The concentration range of the two substances was from 0.39 to 4.29μg·g-1 and from 1.63 to 8984.18μg·g-1 respectively. One drug contained furosemide, while the content was 8.71μg·g-1. [Conclusion]The method established was fast, convenient, had high sensitivity and high accuracy, which can detect prohibited substances quantitatively and qualitatively in diet pills.