A ventilating and noise-reducing apparatus for an indoor transformer is disclosed. The ventilating and noise-reducing apparatus comprises a ventilating louver and an axial flow fan used for performing ventilation and thermal dissipation to ensure a safe and stable operation of the indoor transformer, a multi-channel active control system used for the ventilating louver and mounted on the exterior of the ventilating louver, and a single-channel or multi-channel active control system used for the axial flow fan and mounted on the exterior of the axial flow fan. Due to the ventilating louver and the axial flow fan, the ventilation and thermal dissipation of the indoor transformer are ensured; and meanwhile, due to the active control systems, noise generated by the indoor transformer is restrained from radiating to the outside from the ventilating and thermal dissipating channels.