Abstract: With the main production area of Tongshan Copper Mine turning to the middle section of -613 m and below，the mine ventilation network structure has changed，the air volume distribution of the ventilation system is uneven，the short circuit problem of the air flow is prominent，the ventilation of the deep local operation site is not smooth，and the phenomenon of high temperature and high humidity in the working face is prominent. Therefore，on the basis of completing the detection of ventilation system and the analysis of on-site problems，the optimization and transformation scheme of ventilation system is proposed， and the partition ventilation mode is adopted. The ventilation system is divided into three relatively inde⁃ pendent ventilation areas : the old area above -345 m，the middle area between -388 m and -523 m，and the deep second-stage area below -613 m，and the ventilation structures are set reasonably. A new deep return air project below -568 m is excavated，and a return air auxiliary fan is added on the return air side at -613 m，-658 m and-703 m levels. Using Ventsim three-dimensional simulation software，a three-di⁃ mensional mine ventilation system simulation model is established to simulate and verify the effect of the ventilation system optimization scheme，which provides a basis for the optimization and transformation of the ventilation system. After the optimization，the ventilation system is tested and analyzed. The results show that the stability of the ventilation system is enhanced，and the problem of air flow short circuit is solved. The air volume in the middle section of -613 m and below is increased to 80.33 m³ /s，which meets the air volume required for deep mining，effectively solves the problem of high temperature and high humidity in deep working sites，and ensures the smooth progress of mine safety production.

Key words: ventilation system optimization, partition ventilation, three-dimensional simulation, fan station optimization