Abstract: In the Mayileshan area, western Junggar, northern Xinjiang, Devonian volcaniclastic rocks and the construction of clastic sedimentary rocks are comparative development. In the previous data, they generally were classified as Middle Devonian. In this work, a large number of fossils belonged to Early Devonian were found in the strata, which provided the basis for the age determination of the strata. According to lithostratigraphic units, Devonian was divided into the Lower Devonian Malassu Formation and the Middle Devonian Kourou Moody Formation.