Axi caldera which located in the Early Carboniferous Tulasu—Yielimodun volcanic belt in the west Tianshan Mountains，and occured as a equant geologic body limit e d with circular fault，is 2.6 km in north—south，2.4 km in west—eas t．The caldera which showing its features clearly wi th circular and radial cracks locating at the lip of the crater，the distributio n of the volcanolithofacies，the feature of the geophysic field and so on ， ha s a close genetic relationship to the Axi gold deposit which located in the circ ular fault around the caldera．