Abstract: After years of mining in the underground iron mine in Gansu province，ventilation network has been damaged，resulting in difficulties of air volume adjustment.At present，the mine has been mined to +2 670 m level，and the returning airway atⅠore-body has been damaged in different degrees in +2 715 m level.As the mining levels continue to decline,Ⅰore-body returning air system will be completely destroyed.In the same time，returning airway at Ⅱ ore-body in +2 760 m level has been damaged due to the influence of rock movement，which causes the ventilation system can't meet the requirement of production and seriously influences to the safety production and economic benefit.Based on the current status of mine ventilation and scientific field data measurement，the main existing problems of the ventilation system are analyzed and the optimization reform scheme is proposed as well as the ventilation networks are solved.The optimization reform scheme is based on the mining of existing facilities and equipment，and combined with the expansion of mining scale and the deep mining plan.At the same time，the connection of deep and existing ventilation plans is fully considered，which realizes the expected results and offers scientific basis of mining safe ventilation.

Key words: Ventilation system, Present situation of ventilation, Optimization of transformation, Ventilation network calculating