Abstract： Objective:To establish a method for the determination of chlorothalonil in air by filtration membrane sampling, solvent elution and gas chromatography.Methods:PTFE filter was used for sampling, eluted with dichloromethane, separated by DB-5 capillary column, and determined by FID.Results:The standard curve was used for quantitative detection, and the correlation of chlorothalonil in the range of 15 μg/ml-300 μg/ml, R2=0.9999. The detection limit of this method was 1.70 μg/ml and the lower quantitative limit was 5.70 μg/ml. The minimum detected concentration was 0.045 mg/m 3 (75L air sample was collected) . The recovery rate was 90.14%-91.81%. The precision of the same batch was 1.5%-1.8%, and that of different batches was 2.3%-3.8%. The sampling efficiency can reach above 95%; The samples can be stored for 14 days at room temperature. Conclusion:The results show that the method of filtration membrane sampling-solvent elude-gas chromatography is suitable for the determination of chlorothalonil in the air.