Abstract: In order to optimize the ventilation system of No.12 mining area in Chensilou Coal Mine, according to mine production practice, combined with the using of the main return of the north wing and the belt lane in No.12 mining area, and making full use of the existing production system, the paper proposes the bottom air bridge which has the advantages of little influence on the original production system, less engineering quantity, convenient construction. By taking the control on key links, like as the roadway reinforcement, equipment protection, blasting from the bottom, airflow control, prevention and control on gas, support of steel beam, concrete block and so on, all these ensured the safe, fast and efficient construction of air bridge, and the normal production order of the coal mine at the same time. The project has good effect on supporting stability and reliable ventilation.