The analysis of trace elements of the dark Permian mudstones shows that Ejinaqi and its surrounding areas were semi-salt water sedimentary environment during the Permian.  Combined with the analysis of V/V+Ni and Ceanom of mudstones, it is suggested that Permian period was characteristic of reductive environment and was helpful to the preservation of organic matters. Combination of distributive pattern of the rare earth elements from dark mudstones with field geological survey indicates that its province was from the upper crust and its parent rocks were the mixing of claystones and granite rocks in the studied area.