Abstract: A residual analysis method was established for the simultaneous determination of metamifop and its metabolites HPMFPA, HFMPA, 6-CBO in brown rice, rice hull, rice stalk. The samples were extracted with acetonitrile, and then purified by QuEChERS with primary secondary amine（PSA） and C18 sorbent, and then determined by ultra performance liquid chromatography-triple quadrupole tandem mass spectrometry in select ion monitoring mode with external standard method for quantification. The results showed that the recoveries of metamifop and its metabolites at the addition levels(0.01～0.5 mg·kg^-1) were within 70.1%～108.8%, with the relative standard deviation（RSD, n=5） between 1.8% and 11.9%. The degradation rate of both metamifop and its metabolites was less than 30% during 32 weeks of storage at-18 ℃. The method is simple, fast, accurate and sensitive, which can be used as a practical detection and analysis technique. The storage stability results showed that metamifop and its metabolites were stable in rice samples.