Mogao Cave 3 is representative of Dunhuang caves. The thousand-armed and thousand-eyed Avalokite?vara illustrations on both north and south walls give prominence to the art of line drawing,in which Dunhuang art excels. Cave 3 is generally considered to be constructed in the Yuan dynasty,mainly by scholars from Dunhuang Academy. Recently,scholars have gradually put forth their opinions on the construction date of Cave 3,arguing it dates back to Western Xia. This study carefully examined the inscription left by Shi Xiaoyu in Cave 3,the main evidence for its construction in the Yuan dynasty,considered the contents and artistic styles and features of the murals inside Cave 3,comparatively studied the different features of both Western Xia and Yuan dynasty caves,and finally came to the conclusion that Cave 3 at the Mogao Grottoes was constructed in the Western Xia instead of the Yuan dynasty.