Abstract: This paper studies conodonts (7 genera with 11 species),analysing and discussing its biostratigraphic significance in Yan Guan period at Xiaohaizi,BaChu of XinJiang. The Devonian-Carboniferous boundary is drawn at the position slightly lower than that where iphonodella occurs (the base of middle member of BaChu formation ).It is aslo determined that the original Kalasay formation is actually Yan Guan period deposite, BaChu movement diseribed as a new discovery of interior events of Yan Guan stage in TaBei.

Key words: Yan Guan period, conodonts, animal group, BaChu of XinJiang