The elemental geochemistry and carbon and oxygen isotope characteristics of sedimentary rocks from the Jialingjiang Formation-Leikoupo Formation in the Emeishan area of the Sichuan Basin were analyzed to explore their paleoenvironmental significance and provide basic information for the study of the Early-Middle Triassic paleoenvironment on the northwest margin of the Sichuan Basin. The results show that the samples ∑(CaO+MgO+LOI) ranged from 13.98% to 93.31%, reflecting a relatively turbulent sedimentary environment. The data show that the variation range of δ¹³C value is from -6.95‰ to 0.36‰, and the variation range of δ¹⁸O value is from -9.06‰ to -0.99‰. The overall performance trend of δ¹³C value is decreasing-increasing-decreasing-increasing. The seawater salinity shows a multi-stage change of rising, then decreasing, and then rising again; the seawater temperature ranges from 7.11 to 34.94℃, with an average temperature of 21.99℃, and the ancient seawater temperature experiences a trend of decreasing-increasing-decreasing, with a sharp increase in temperature near the Early-Middle Triassic boundary. The study area as a whole is in an oxidized sedimentary environment, with intermittent occurrences of oxygen-poor sedimentary environments. The above geochemical indicators are well coupled and consistently reflect a relatively humid-relatively dry and hot-relatively humid marine depositional environment in the Early-Middle Triassic boundary of the study area.