Abstract: NATM and mining method are often adopted in the construction of underground caverns, the pollutant produced by blasting at working face affects safety and occupational health of workers and restricts the advance rate.Based on the Baihetan hydropower station project, the design concepts of " three-in-one combination" and "design by stages" for the construction ventilation system are proposed, a three-dimensional unsteady turbulent field model is established, the characteristics and law of smoke emission during ventilation of complex underground cavern group are studied, special ventilation tunnel connecting to the main caverns is planned and an energy-efficient“ air supplying + air exhausting”ventilation system is formed, the frequency conversion fan is adopted to realize the optimal effect of mechanical ventilation based on use of natural ventilation. The numerical calculation and test results of pollutant concentration at site show that air distributes smoothly, the air velocity in the vertical shaft area is much larger than that near the cavern group, the emission paths of pollutant are working face, ventilation shaft and special ventilation adit, the pollutant produced by blasting can be fully discharged after 15 minutes of ventilation.