Abstract: Longqiao Iron Mine is designed with an annual production capacity of 3 million tons and adopts a two-wing diagonal exhaust ventilation system with a designed air volume of 372 m³/s. As the main mining area is gradually transferred to the eastern and deep parts of the mine，problems such as unbal‐ anced air distribution in the western area，poor air return east of Line 3，insufficient air supply in the deep parts，and low utilization rate of return air structures are encountered in the ventilation system of Longqiao Iron Mine.Based on the actual status of the ventilation system and field measurements，an adjustment idea of "increasing resistance and boosting pressure" is proposed. The overall efficiency of the mine ventilation system is improved through systematic measures including the addition of auxiliary fans for air intake and return，the establishment of a simulation model for the stope air return path，the implementation of central‐ ized negative pressure regulation in mining areas，and the optimization of the ventilation network.A three�dimensional simulation software is used to conduct network calculation and effect verification for the opti‐ mized scheme. The results show that the air volume required by each mining area is satisfied.After the opti‐ mization of the ventilation system in Longqiao Iron Mine，the return air volume of the eastern mining area is 100.64 m³/s，which is increased by 33.45 m³/s. The return air volume of the western mining area is 128.49 m³/s，which is increased by 57.9 m³/s. The air supply volume in the deep part is 171.01 m³/s， which is increased by 125.42 m³/s. The expected target is achieved.This research can provide technical ref‐ erences for the optimization and adjustment of ventilation systems in large-scale underground mines with multi-level and multi-shaft mining conditions.

Key words: ventilation system optimization, three-dimensional simulation, ventilation network calcu‐ lation, multi-level mining