Evaporites and carbonates intercalated with volcanic beds are distributed in the Jialingjiang and Leikoupo Formations straddling the boundary of the Lower and Middle Triassic in the Sichuan Basin. High-resolution curves of 87Sr/86Sr ratios and δ34Ssulphate of marine sediments show the study section has relatively stable isotopic compositions of S and Sr except for the volcanic bed. The abrupt positive shift of 87Sr/86Sr ratios and negative shift of δ34Ssulphate occurred in the volcanic layer. The Sr isotopic curve defines a rough age range of 244 to 248 Ma. The volcanic bed is characterized by high anhydrite Th/U ratios, indicating a strong anoxic environment. The volcanic eruptions released a huge amount of CO2 and SO2, which could lower temperature first by sulphate aerosols and induce subsequent climate warming by greenhouse gases. This cooling-warming cycle has triggered the overturn of the deep anoxia seawater. The synergistic effects of degassing of gases (CO2 and SO2) and overturn of the deep anoxia seawater have caused the negative shifts of δ34Ssulphate, and anoxic event during the volcanic eruption. Meanwhile, volcanic eruptions and associated acid rain could have enhanced the continental weathering, resulting in an increasing flux of radiogenic 87Sr. Furthermore, volcanic eruptions and related environmental changes could have imposed severe stress on the full recovery of the ecosystem since the End-Permian mass extinction, which is corroborated by fossil records.