It is necessary to analyze each factor that affects the stability of mine ventilation system in order to comprehensively and quantitatively analysis the stability of mine ventilation system. Piston wind velocity engendered by hoisting system is one of the primary factors. Using Bernoulli equation and continuity equation of non-steady flow, the paper presents the calculation formula of piston wind velocity in mine hoisting systems by assuming different passing section. According to the formula, piston wind velocity can be quantitatively calculate, which will be used as basic data for the stability analysis of mine ventilation system. In this way, the stability of mine ventilation system can be further analyzed, which will benefit the safety of productien.