Abstract: Beiminghe Iron Mine is a large underground black mine.It adopts the sublevel caving method without bottom pillar.The ventilation system adopts the central diagonal fourstage base station ventilation method.The two wings of the ore body enter the air and the middle return air.With the continuous downward movement of mining depth and the continuous change of ventilation network,there are some problems in the current ventilation system,such as insufficient total air volume,unreasonable air distribution in the middle section,pollution air circulation in the mining area,etc..By using the optimization technology of ventilation system and air volume control technology,the optimization measures of ventilation system adjustment are put forward to solve the above problems.Through the comprehensive comparison of the three ventilation system adjustment and optimization schemes,the final choice is to add the main air inlet fan at the stone gate of the west air shaft,and to coordinate the operation conditions of the main air inlet and return fans.The threedimensional ventilation system calculation program is used to calculate the optimization scheme,and then the field debugging is carried out according to the calculation results.It is determined that the operating frequency of two parallel fans in -50 m horizontal return fan station is 40 Hz/43 Hz.When the operating frequency of four fans in -230 m east and west inlet fan stations is 30 Hz,the operation conditions of the main fans of the inlet and return fans are in good coordination,and the total air volume of the system reaches 193 m3/s,which meets the theoretical requirements.The calculated total airvolume of the mine is 180 m3/s.At the same time,the problem of waste air circulation in the mining area is solved,and the ventilation effect of the mine is obviously improved.