Abstract: The Upper Triassic Xujiahe Formation was first reported in the Tianquan Lushan Baoxing area,Sichuan province.It contains abundant bivalve faunas.The depositional environment of this formation may be divided into the delta distributary channel microfacies,interdistributary swamp and lake microfacies and delta interdistributary bay microfacies.Its study may provide new evidence for the analysis of the formation age of the Sichuan inland basin.