Abstract: The volatilities of four pesticides from vegetable, water and soil surfaces under laboratory modelling system were studied. The results show that the orders for the volatile rate of the pesticide in different mediums are methyl-ISP > pyrimyxthion > propachlor> monocarboxoldepyde. The results of the theoretical calculation and the actual analysis are almost the same. According to the criteria of pesticide safety evaluation, these four pesticides are classified to low volatility pesticide.