In order to demonstrate science and feasibility of 8303 (east) working face with large mining depth technology of No. 1 Mine of Yangquan Mining Group, based on the tested mining of 8310 and 8303 ( west ) with large mining depth, the influenced factors of large mining depth under complex geological condition were analyzed, the stability of upper overlying roof thickness, variability of geological conditions and tectonic development were demonstrated, the large mining depth technology was advised to adjust to fully mechanized caving technology.