Abstract: Researches on core, outcrop observation and thin section identification show that near-shore underwater fan and lacustrine deposits are mainly found in the Middle Permian Lucaogou formation on the periphery of Bogda Mountain, and mixed deposits are mainly distributed in the margin of the near-shore underwater fan and semi-deep—deep lakes. 2 kinds of mixed depositional sequences that consist of conglomerate, sandstone, intraclast limestone and mudstone, and conglomerate, conglomeratic micrite and mudstone, respectively are developed in the margin of the near-shore underwater fan; the other two mixed depositional sequences that consist of limy siltstone and mudstone, and mudstone, micritic dolomite and micrite, respectively are developed in semi-deep—deep lakes. Sr/Cu ratio indicates that the depositional stage of Lucaogou formation in the study area was dominated by tropical and dry climate with intermittent warm and humid climate, the alternation of the 2 climates was the root cause of the wide development of the mixed rocks and mixed sequences. Tectonic movement controls the properties of the basin in the study area, which influences the type and characteristics of the mixed sedimentary facies in Lucaogou formation, and the rise and fall of lake level and the supply of sediment sources further control the mixing of terrigenous clastics with carbonate components. On the basis of the study on the characteristics and the controls on the mixed deposits and combining the characteristics of rock, rock assemblage and sedimentary structures, the paper establishes a model of the mixed deposits of Lucaogou formation.