The invention discloses a hydropower station ventilating system. The system comprises a volute layer (1), a turbine floor (2), an interlayer (3) and a generator floor (4) which are arranged from bottom to top. A ventilating port (11) is formed in the surface where the interlayer (3) and the generator floor (4) are partitioned. An air supply outlet (6) is formed in the volute layer (1) and connected with a refrigerating device (5). A bus tunnel (10) is formed in the interlayer (3). The volute layer (1) communicates with the interlayer (3) and the generator floor (4) through a second ventilatingpipeline (8). The turbine floor (2) communicates with the interlayer (3) and the generator floor (4) through a first ventilating pipeline (7). The volute layer (1) communicates with the turbine floor(2) through a third ventilating pipeline (9). According to the hydropower station ventilating system provided by the invention, the problems of a low temperature and moisture of the volute layer canbe solved, and the heat dissipating effect of the generator floor is good.