Abstract: In order to explore the synergistic effects of acidification and environmental pollutant phenanthrene (PHE) on Chinese mitten crabs (Eriocheir sinensis), we carried out a 14-day joint exposure experiment of E. sinensis (15.0±2.3) g to different pH (5.5, 6.5, 7.8) and PHE (0, 50 µg·L⁻¹). The results show that: 1) Under the synergistic treatment of pH 5.5×PHE 50 on E. sinensis, the hepatopancreas and gill tissues were severely damaged; the shape of the hepatopancreatic tubules changed; a large number of vacuoles appeared in the atrophy of the hepatic duct cells. The gill axis was enlarged; the cuticle of the gill filament was damaged; the local basement membrane was ruptured. However, pH 6.5×PHE 50 did not significantly damage the hepatopancreas and gill tissues of E. sinensis. 2) PHE treatment significantly reduced the contents of Gly and LDL-C in hepatopancreas of juvenile E. sinensis, indicating that PHE could decrease the energy metabolism level of E. sinensis. Compared with the control group, pH 5.5×PHE 50 inhibited the contents of TG, Gly, HDL-C and LDL-C, while pH 6.5×PHE 50 significantly increased TG content. 3) Real-time fluorescent quantitative PCR experiment shows that AHR, ARNT and CYP1A1 increased significantly with the decrease of pH, and reached the highest values at pH 5.5. The results reveal that the combining effect of acidification and PHE changes the energy metabolism of E. sinensis, and pH 5.5 significantly aggravates the toxic effect of PHE on the hepatopancreas tissue structure of E. sinensis, as well as its energy metabolism.