Abstract: Abstract：This paper deals mainly with sedimentary media environment of Late Triassic epoch in the middle part of western Ordos Basin through identifying the corresponding relationships between trace element compositions and sedimentary media environment on the basis of analytical results of some special trace elements such as Sr, Cu, Ba, U, Ti, V and Ni which are sensitive to sedimentary media environment. The results of the study show that the sedimentary media environment of Late Triassic epoch from Chang-9 to Chang-7 was warm humid climate in general and tended to become increasingly warm and humid in upward direction, indicating the brackish water phase of the freshwater environment with a slight increase in salinity of Chang-7. The redox condition from Chang-9 to Chang-8 was normal, while that of Chang-7 became anoxic. The vertical variation of water column stratification is not obvious from Chang-9 to Chang-7.