The sorption of alachlor is one of the most important behaviors of transference and transformation of alachlor in soils,and it also plays significant role in the soil environment.Three soil samples were collected from the suburb farmland of Jiamusi(S1),Yilan(S2) and Harbin(S3) along the Songhua River(Northeast,China),and batch experiments were conducted to investigate the effects of dissolved organic matter(DOM) on the adsorption-desorption behavior of alachlor in soil-water system.The results showed that the adsorption capacity of alachlor was suppressed significantly after adding DOM into soil-water system,yet the DOM might accelerate the desorption process of alachlor from soil.The adsorption and desorption isotherms for alachlor in the soil samples were found to fit well with the Freundlich model(R2>0.858)and the order of adsorption capacity of the soil samples was in the order of S1>S2>S3.Hysteresis Index showed that the hysteresis existed in the adsorption-desorption process of alachlor.