Abstract: A method of HPLC-IMS/MS for determination of chlormequat in agricultural products was proposed. The sample was extracted with methanol-water (1+1) and hexane,and purified with a cation exchange solid-phase extraction column. The eluate was separated by isocratic elution using a mixed packing chromatogram column with cation exchange resin and C18 as stationary phase,and 10 mmol·L-1 ammonium acetate-acetonitrile solution containing 0.1% (φ) acetic acid as mobile phase. ESI+ and MRM were adopted in MS/MS detection,and internal standard method was used for quantization. Linearity range of chlormequat was found between 1.0-100 μg·L-1,the detection limit (3S/N) was 5 μg·kg-1 and the quantitation limit was 10 μg·kg-1. Tests for recovery were made by addition of 10,100,500 μg·kg-1 of chlormequat,giving values of recovery in the range of 90.5%-98.5% and values of RSD′s (n=6) in the range of 0.99%-2.2%.