Abstract: An analytical method for the simultaneous determination of 73 pesticides in Hirudo using gas chromatography-tandem mass spectrometry(GC-MS/MS) and QuEChERS procedure was developed. After being soaked in water, the samples were extracted with acidic acetonitrile and cleaned up by a mixture of sorbents (150 mg PSA and 150 mg C₁₈). In order to obtain the optimum recovery rate of pesticide analysis, the amounts of the adsorbents were investigated. The analytes were separated by a HP-5 MS column connected to an electron impact ion source(EI) with dynamic multi-reaction monitoring MS mode. Under the optimized conditions, the results showed that the 73 pesticides had good linearity within the range of 10.0-500 μg/L, with correlation coefficients(r) higher than 0.99. The average recoveries ranged from 71%-117%, and the relative standard deviation(RSD) was 1.1%-12% (n=6) at three spiking levels (0.02, 0.04 and 0.2 mg/kg). The LOQs were 0.02 mg/kg and LODs were 0.001-0.008 mg/kg. The method is simple, sensitive, reliable, and can meet the requirements of practical detection for pesticides.