Abstract: A method for the determination of MCPA residue in wheat samples was developed using high performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS). The preparation procedure of sample was also applied to determine the MCPA residue in soil (with HPLC-UVD). The sample was extracted with 0.04 mol/L NaOH, adjusted pH value below 3 with phosphoric acid. Liquid-liquid partitioning with ethyl acetate, and further cleanup by graphitized carbon black (GCB) were followed. The mass spectrometer with interface of electro-spray in negative ion mode (ESI-) was operated in multi-reaction monitoring (MRM) mode. The precursor／product ion transitions (199／141 m/z) were monitored. Average fortified recoveries ranged from 75.0%-112.1% with relative standard deviations 2.7%-14.8% in plants, wheat and straw samples. Lower Practical Levels (LPL) were 0.5 mg/kg for straw, 0.05 mg/kg for wheat, and 0.5 mg/kg for wheat plants, respectively. The method was used to determine MCPA residues in various matrices from supervised residue field trials in China.