Abstract: Ventilation during construction of underground hydropower houses has serious effects on construction efficiency and safety. This paper describes a 3D unsteady Euler two-phase turbulence model considering the effect of gas-solid interaction force, aiming at difficulties in dust discharge caused by complex structure with inter-connected tunnels. We have applied this model in a case study of the ventilation in drill-blasting construction for an underground hydropower house in China and analyzed the airflow structure and dust migration. The analysis reveals a relationship of dust distribution versus ventilation time and an eddy zone that forms near the working face and hinders dust discharge. A comparison of two different working faces shows similar airflow structures near them. For the ventilation scheme studied, dust concentration in the main powerhouse is significantly reduced with a longer ventilating operation, and it can meet the safety standard if ventilating operation takes roughly 1300s. The peak of dust concentration migrates continuously toward the tunnel outlet and its amplitude decreases with time.