Abstract: An ameliorated pretreatment method for determination of polychlorinated biphenyls（PCBs）in tissues of dolphin has been established. After pretreated in turn by the extraction, purifying for the high-fat tissues and low-fat tissues of dolphin samples, the PCBs were determined by a gas chromatography (Agilent 6890N) equipped with an ECD (electron capture detector). Identification and quantification of PCBs were performed by retention time and external standard method respectively. The results showed that the recovery was between 75.8% and 119.2%, the coefficient of variation was 5.6%~11.2%, and the detection limits of the method were 0.126~0.642 ngg-1. The data of accuracy and repeatability are satisfied for analysis on the trace amounts of organic contaminants in marine organisms. The results of practical analysis for dolphin samples showed that the method was suitable to determine the contents of the PCBs in the dolphins.