A typical irrigation area was selected as objective study area which has more than forty years history with wastewater irrigation in northeast China. Acquiring relevant data and model parameters, the soil—air exchange of organochlorine pesticides and its fractionation effect were deeply disscussed with application of fugacity approach. The results show that, in the certain cases of soil organic matters, the difference of soil—air partition coefficient (KSA) between HCHs and DDTs has one order of magnitude at daily average maximum temperature higher than at daily average minimum temperature; HCHs released into environment for secondary distribution more easily than DDTs. The rate of change of KSA value is different when every 1% enhanced in soil organic matter and gradually stabilizing with enhanced soil organic matter content. There is a negative correlationship between octanol-air partition coefficient (KOA) and fugacity fraction (ff ) of soil—air exchange, the correlation coefficients are: R=-0.743 (P<0.05),R=-0.763 (P<0.05), R=-0.776 (P<0.05) when soil organic matters are 1%, 2% and 3%, respectively. Application of ratio between soil and air concentration (Cs/a), in the constant cases of other parameters, the soil and air concentration will affect the soil—air exchange of HCHs and DDTs. The primary and secondary fractionation effect of HCHs and DDTs further suggested that the soil properties and physical—chemical properties will affect their fractionation effect.