Abstract: A method of determination of arsenic, cadmium, lead, chromium and mercury in organic fertilizer was proposed by ICP-MS coupled with microwave digestion. The sample of organic fertilizer (0.200 0-0.500 0 g) was treated with 10 mL of HNO₃ and 1 mL of H₂O₂ solution in a microwave digestor under programmed temperature elevation. The digested solution was evaporated to 2 mL, and HNO₃ (1+99) solution was added to the digested solution to make up its volume to 50 mL for use as sample solution. Elements of arsenic, cadmium, lead, chromium and mercury in the sample solution were determined by ICP-MS. Values of detection limits (3.3s/k) were in the range of 0.015-0.040 mg·kg^-1, and Values of RSDs (n=6) were all less than 5.0%. Test for recovery was made by standard addition method, giving results in the range of 98.0%-101%.