Abstract: A study on dynamics and long-term fate of residual hexachlorocyclohexane(HCH)in aquatic and terrestrial environments in Ya-Er Lake Area,heavily pollutedby HCH historically, was carried out during the period from 1990-1993. Theconcentration Kinetics and half-lived bine of HCH-residues in four differentenvironments were obtained. The results show that sediment is the primaryaccumulation site for the long-term fate of HCH-residues. Despite HCH was bannedfor more than ten years in Ya-Er Lake Area,the bioaccumulation of HCH-residue infreshwater food chain was still high (BCF=104 in fish liver). The distribution andmobility of HCH-residues are correlated with the organic matter positively. TheHCH-residue in the current environmentin that area is mainlyβ-HCH. Meanwhile, aseries of model exponential equations are used for describing dynamics of HCH-residues. From these equations, the half-lived time calculated and the order infour different environments are:water soil mud of paddy field sediment.