Abstract: In large-scale mines，the subsequent filling method for staged mining room with larger production capacity is often adopted. This mining method uses medium-deep hole or large-diameter deep hole blasting for ore dropping. During the second step mining room mining，the impact load generated by medium-deep hole or large-diameter deep hole blasting is prone to cause the collapse of the filling body， seriously threatening the safety of the mine house mining operation. To solve this technical problem，the re‐ search first calculated the strength required for the self-standing of the filling body of Makeng Iron Mine through six differentiated empirical formulas，combined with the physical parameters of the filling body and the ore and rock，and initially screened the strength threshold of the first step filling body based on the safety factor. Secondly，based on the theory of transmission stress of blasting shock waves，the quantitative relationship between the charge quantity，the distance between the blast core (thickness of protective wall) and the damage of the filling body is established. The transmission stress of shock waves during blasting in medium-deep holes and large-diameter deep holes is calculated respectively to determine the required strength of the filling body to resist blasting impact. Finally，the reasonable strength of the filling body un‐ der blasting load conditions is determined. Finally，industrial tests of ore house mining blasting were carried out in the second step ore houses of 6-3-4P (medium-deep hole) and 60-2P (large-diameter deep hole) of Makeng Iron Mine. Through three-dimensional scanning of the goaf，the collapse and mixing rate of the fill‐ ing body were determined，and the reasonable parameters of the strength of the filling body and the retain‐ ing wall were verified. The research results show that when the height of the mining room is 72 m and the width is 15 m，the maximum self-standing strength of the filling body calculated by six empirical formulas is 2.22 MPa. Under the condition of considering the influence of blasting impact on the filling body，for the medium-deep hole blasting with a maximum charge of 100 kg for the side hole，when the wall thickness is 1.3 m and 2 m，the corresponding shock wave transmission stresses are 2.4 MPa and 1.7 MPa respectively. For large-diameter deep hole blasting with a maximum charge of 294 kg at the side hole，when the thick‐ ness of the protective wall is 1.87 m and 2.9 m，the corresponding shock wave transmission stresses are 2.4 MPa and 1.7 MPa respectively. Based on the research results，industrial tests of blasting for mining room mining were conducted. The collapse and mixture rate of the filling body in the medium-deep hole mining room was 1.17%，and that in the large-diameter deep hole mine house was 7.6%，both meeting the requirements for safe mining. Taking into account the self-standing strength of the filling body，the devia‐ tion of the blast hole，and the influence of the blasting load，the reasonable strength of the subsequent fill‐ ing body of the staged mining room is finally determined to be 2.4 MPa. The thickness of the filling body wall reserved for the blasting drop of medium and deep holes is 1.3~2 m，and that for the blasting drop of large diameter deep holes is 1.9~2.9 m. The parameters can effectively balance the self-sufficiency of the filling body and its resistance to blasting impact，providing a technical reference for the second step mining room mining of similar large-scale mines.

Key words: subsequent filling method, strength of filling body, blasting impact, thickness of protec‐ tion wall