Abstract: In order to solve the problems of high ore loss and dilution and low recovery rate caused by high yield of large block in the middle and deep hole in Heishan Iron Mine，the main causes of large block in the mine are studied by combining field investigation and grey correlation analysis. The high yield of bulk is mainly caused by four factors: ① The single consumption of explosive is small and there is a series of initiation in the process of detonation. ② The original caved bulk ore can not be effectively crushed and blocked the ore outlet. ③ The forming quality of medium-deep hole is low. ④ Large rocks of overburden were mixed into caved ore heap in advance. Based on this，a series of bulk control methods were proposed to optimize the single consumption and minimum resistance line of explosives，refine ore extraction in zoning sections and strengthen the quality management of medium and deep hole formation. Through the field test，the underground bulk rate is reduced by 4%.The recovery rate is increased by 1.32%，and the qualified rate of medium-deep hole is increased by 5%，which realizes the effective control of the medium-deep hole falling large block in Heishan Iron Mine，and can provide technical guidance and reference for the production mines under similar conditions.

Key words: pillarless sublevel caving method, large block, mid-deep hole, blasting parameters, ore drawing control