Abstract: The changes of ultrastructures of hepatic cells of Boleophthalmus pectinirostris were investigated after the fish were exposed under benzo (a) pyrene in different concentrations under experimental condition.The results showed that the organelles in hepatic cells of B.pectinirostris were damaged to different extents after the fish was exposed under lower concentration of BaP (0.5 mg稬^-1) for up to 7 d, in which, mitochondria and endo-plasmic reticulum were the chief organelles affected by BaP exposure.While the fish was exposed under higher concentration of BaP (5 mg稬^-1) for 2 h, almost all of the organelles including mitochondria and endoplasmic reticulum in hepatic cells of B.pectinirostr were affected by BaP exposure.The structures of liver cells were seriously damaged.It was demonstrated that BaP could produce multiorganalle lesions in hepatic cells of B.pectinirostris, and the severity extent of such lesions was dependent on the concentration level of BaP.