Glutathione S-transferases (GST) play a prominent role in protecting cells against oxidative stress. Our previous study showed that the reactive oxygen species (ROS) generated from pentachlorophenol (PCP) could cause an acute impact on freshwater bivalve Anodonta Woodiana, but its chronic toxicity remain unclear. In order to investigate the chronic effect of PCP, clams A. Woodiana were randomly grouped into PCP treated group in which animals were administrated with 13.9 μg/L concentrations of PCP, and control group those with similar volume dimethyl sulfoxide. In addition, two complete GST sequences were isolated from A. Woodianaa and respectively named AwGST1 and AwGST2. The full-length cDNA of AwGST1 was consisted of a 5′ untranslated region (UTR) of 132 bp, a 3′ UTR of 80 bp and an open reading frame (ORF) of 609 bp encoding a polypeptide of 203 amino acids. The full-length cDNA of AwGST2 contained a 5′ UTR of 57 bp, a 3′ UTR of 291 bp and an ORF of 678 bp encoding a polypeptide of 226 amino acids. The constitutive expression levels of AwGST1 and AwGST2 were examined in different tissues including foot, mantle, adductor muscle, heart, hepatopancreas, hemocytes and gill. Administration of PCP could result in a significant increase of AwGST1 and AwGST2 expression in the hepatopancreas, gill and hemocytes. In the hepatopancreas, AwGST1 mRNA levels of PCP treated group increased more than 28.73% at day 1, then 70.37% (P < 0.05) at day 3, reach to 6.64 times (P < 0.01) at day 15 in contrasted with that of control group. AwGST2 increased more 18.18%, 82.88% (P < 0.05) and 2.43 times (P < 0.01) at day 1, 3 and 15, respectively. In the gill, AwGST1 expression showed a significant up-regulation in the PCP treated group during experiment observed compared with that of control group, mRNA level of AwGST2 increased more than 1.44 times (P < 0.05). In addition, expressions of AwGST1 and AwGST2 were significantly induced after PCP treatment in the hemocytes. These results indicated that up-regulations of AwGST1 and AwGST2 expression in bivalve A. woodiana are contribute to against oxidative stress derived from PCP treatment during experiment observed.