Abstract: On the basis of previous studies,by integrated use of rock stratigraphy,biostratigraphy principles and methods,starting from drilling and outcrop,according to new infor-mation obtained fossils,combined with lithology,tectonic movement,Yining depression Triassic rocks,the biostratigraphy has been studied for the first time.The results show that Yining depression is lack of Triassic,the introduction of the northwestern margin of the Junggar basin system has been proposed in the area of rock formations.From bottom to up,middle Triassic Karamay group and upper Triassic Baijiantan group were developed.Yining depression Triassic fossil pollen fossils can establish two combinations,combinationsⅠ for Aratrisporites-Piceaepollenites-Chordasporites portfolio,during Middle Triassic era,the combinationⅡ for Piceaepollenites-Dictyophyllidites-Colpetopollis portfolio,during the Late Triassic.