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 δ³⁴S_sulphate 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 δ³⁴S_sulphate 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 δ³⁴S_sulphate, 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.