The Qitadaban Formation of the Qingbaikou System, Neoproterozoic, is an important component of metamorphic basement in the western part of the Central Qilian Block, being of great significance to understanding the Proterozoic geological and tectonic evolution of the Qilian Block. The research work on dacite tuff of the Qitadaban Formation has been carried out in this paper. Methods: Based on the field work, we finished microscope observation, whole- rock geochemical analysis and LA- ICP- MS zircon U- Pb dating for the dacitic tuff in this paper. Results: The zircons from the rock can be divided into three groups in age. Combined with regional geological data, it is considered that the first and the second age groups of zircons (1408~1410 Ma, 1018~1021 Ma) from the dacitic tuff are responding to the Columbia supercontinent breakup and Rodinia continental convergence (Greenwell Orogeny) in the Qilian Block. The third group of zircons (946~964 Ma) has a mean- weighted n(206Pb)/n(238U) age of 958±3 Ma (MSWD=1. 4), interpreted as the formation age of the tuff. Petrogeochemical analysis shows that the dacitic tuffs are peraluminous (A/CNK=1. 37~1. 75), high potassium (K2O>Na2O, K2O=4. 48%~4. 86%) and calc- alkaline (σ=0. 89~1. 26). The ΣREE=149. 7×10-6~156. 4×10-6 , (La/Yb)N=10. 15～10. 61, and δEu=0. 62~0. 63; with enrichment in large ion lithophile elements (K, Rb, Ba, Th) and deplation in high field strength elements (Nb, Ti). Conclusions: The dacite tuff show similar characteristics with island arc calc- alkaline volcanic rocks in geochemical composition. Thus, they formed in an active continental margin environment and was a response to the formation of the Rodinia supercontinent in the early Neoproterozoic in the Qilian Block.