Abstract: The surface subsidence range induced by underground mining is commonly predicted by angle of breakage, and this traditional method is not suitable for deep ore-body mining. The actual subsidence range was measured in Gongchangling iron mine and the lateral abutment stress from the moving loosened medium in the subsidence pit was analyzed. As a result, it is showed that the range of surface subsidence is mainly controlled by a critical medium column that could sustain the stability of lateral rock mass, and the factors related to the height of critical medium column are stability of surrounding rockmass, angle of mined-out area, internal friction angle of granular media and the bulking coefficient of rockmass. Accordingly, the measure to controlling surface subsidence range is proposed, and timely backfilling of the subsidence pit with some solid waste materials obtained from the mine production could decrease the critical depth. A formula of subsidence angle is derived from the relation between angle of breakage, depth of mining and height of critical medium column.