Abstract: The exploration practice in recent years shows that a broad prospect appears for exploration of Shishugou group of Jurassic in east-em Junggar basin. But now something is in question about its sequence classification. The div iding criterion of south-north outerop sections are not the same; the southern wells differ from outcrop in dividing criterion,whereas the northern wells have not been divided in terms of available sequences. This paper analyzes the evolution of structure, paleo-environment and paleo-climate in this area, takes the rock color and sedimentary cycle as the primary bases for dividing Shishugou group into Qigu formation and Toutunhe formation, and thus solves the di-viding problems between wells and outcrops in Qigu and Toutunhe formations in east Junggar basin. it is suggested that the previous criterion that uses tuff to divide these two formations should be repealed.

Key words: Junggar basin, Jurassic, stratigraphic classification, standard, tuff