Glutathione S-transferase (GSTs, EC 2.5.1.18), a class of multifunctional detoxification enzymes widely distributed in organisms, is involved in the metabolism of many toxic substances from both internal and external sources, and plays an important role in protecting cells against biological and abiotic stresses. This study investigated the characteristics of the Ruditapes philippinarum gene family (RpGST) and its function in response to acute hypersalinity and acute hyposalinity stress. Bioinformatics methods were used to identify RpGST gene family members and analyze their structural characteristics, chromosome localization, phylogeny, and expression characteristics in the hepatopancreas after acute salt stress. A total of seven RpGST genes were identified, namely GSTA1, GSTA2, GSTA3, GSTA4, GST_C_3a, GST_N_M1, and GST_N_M2. Chromosome localization results revealed that these seven GST genes were located on five chromosomes. The hydrophobicity analysis showed that all protein members had different degrees of hydrophilicity. The average aliphatic amino acid index was 82.08; subcellular localization found that RpGST proteins were all located in the cytoplasm; and all members of this gene family possess the glutathione transferase domain (PF00043, PF02798), which is associated with antioxidant and detoxification functions. Phylogenetic analysis revealed that RpGSTs were divided into three subfamilies and were evolutionarily conserved. The seven RpGSTs were divided into three distinct classes, with the GSTA class being the largest, consisting of four members within the Ruditapes philippinarum family, whereas the GSTM class consisted of two members and the GST_C_3 class of one member. All GSTs in the Ruditapes philippinarum family evolved into separate clusters, such as RpGSTA and RpGSTM, related to the wide distribution and strong adaptability of the family. These results can provide a reference for the subsequent breeding of Ruditapes philippinarum with high and low salinity tolerance. After acute salinity stress in Ruditapes philippinarum for 0 h, 12 h and 24 h, the hepatopancreatic expression levels of RpGST members in acute hypersaline (40) and hyposaline (15) stress were detected by qRT-PCR. The results evidenced that the relative expression levels of RpGSTA1, RpGSTA2, RpGST_N_M1, and RpGST_N_M2 in the hepatopancreas of Ruditapes philippinarum increased with time, and the expression levels of RpGSTA1 and RpGSTM2 were significantly different from those of the control group (P＜0.01), whereas the relative expression levels of RpGSTA3, RpGSTA4 and Rp GST_C_3a first decreased and subsequently increased. The relative hepatopancreatic expression levels of RpGSTA1, RpGSTA4, RpGST_C_3a, RpGST_N_M1, and RpGST_N_M2 in Ruditapes philippinarum increased over time under acute hyposaline stress. Specifically, those of RpGSTA1 and RpGSTA4 significantly changed during acute hyposaline stress, gradually increasing with time, and this difference was significant compared with the control group (P＜0.05). In contrast, the relative expression levels of RpGSTA2 initially decreased and subsequently increased over time, while the relative expression of RpGSTA3 first increased and then decreased. The expression of glutathione transferase under acute low-salt stress was significantly higher than that under acute high-salt stress, indicating that acute low-salt stress had a more pronounced effect on Philippine clams than acute high-salt stress. This study clarified the gene characteristics, phylogeny and response mechanism of the RpGST gene family in the context of acute hypersaline and hyposaline stress. It enriches the research data on the RpGST gene family in bivalve shellfish and provides a reference for further study on the role of this gene family in regulating salinity stress.