Abstract: In order to optimize the pretreatment method for the detection of cyromazine residues in cowpeas, with the cowpea as the substrate, the comparative test of recovery was carried out between the QuEChERS method and the test method in NY/T 1725-2009 ″Determination of cyromazine residues in vegetables by high performance liquid chromatography″. According to the principle of single variable, the usage of the two cleaning agents PSA and GCB in the QuEChERS method was optimized. The results showed that the standard recovery rate of cowpea samples pretreated with the QuEChERS method was 76.7%-80.3%, and the standard deviation was 6.2%-8.7%. The recovery and precision could both meet the requirements of analysis and detection. The optimal combination of cleaning agents in the QuEChERS method was that the anhydrous magnesium sulfate 900 mg+PSA 100 mg, and the recovery rate of cowpea samples pretreated with the combination of cleaning agents in the QuEChERS method was 83.3%- 86.7%, and the standard deviation was 8.2%-11.5%. In conclusion, the pretreatment method of QuEChERS was simple, rapid, accurate and reliable, which could not only meet the technical requirements for the detection of cyromazine residues in cowpeas, but also be used for the rapid detection of a large number of samples.