Abstract: To analyze the strength requirements of infill bodies under the influence of faults, with the fault occurrence characteristics of a certain mine as the engineering background, the mechanics derivation method was used to focus on the mechanical analysis of the two-step mining near the fault, and the calculation formula for the strength requirements of infill bodies was proposed. Meantime, the FLAC^3D software was used to conduct numerical simulation research on the stability of the infill bodies and ore body at the fault, and the simulation solution of the strength requirements of the infill bodies was obtained. By comparing and analyzing the two calculation results, the reasonable strength requirements of the infill bodies were determined, ensuring the safety and high-efficiency mining of the ore body at the fault. This study can provide reference for the calculation of infill body strength requirement optimization in similar mines.