AY area which shows a monoclinal structure in the direction of northwest is located in the central part of gentle structure zone, Central Sichuan Basin, Southwest China. This paper carried out seismic sequence research of the Upper Triassic Xujiahe Formation with comprehensive analysis of geological, seismic and well logging data. The result shows that the source of the Xujiahe Formation may be located in the south or southeast of the AY area by means of analyzing onlap direction of seismic event, TWT thickness contour map of seismic sequences and incised valley trend. Sandstone composition data excluded the possibility that Luzhou paleo-uplift become the provenance. We supposed that “Qianzhong ancient land” and “Jiangnan ancient land” may be the source of the Xujiahe Formation in Central Sichuan Basin. This viewpoint gives some hints to the further exploration and prospect of the Xujiahe Formation in Sichuan Basin.