Abstract: The dynamic of accumulation in fish was studied both in field and in laboratory. The results show that residues level in fish is largely controlled through a solubility equilibrium with the residue level in water and fish. Experiments show that fish may take up BHC directly from water via gills. When fish reared in BHC contaminated water were removed to a clean pond, their BHC residue began to decrease through elimination into the surrounding water. The percentage of elimination may be expressed by R= b(1—e-ctkt). The rate of elimination is closely related to water temperature. When water temperature is lower than 10℃, the rate of BHC elimination is very slow.