The invention discloses a device for controlling heat dissipation of a switching power module. The device comprises a heat-dissipating fan, wherein the heat-dissipating fan comprises a fan frame, and a stator and a rotor which are accommodated inside the fan frame; the rotor can rotate relative to the stator; a wheel hub and a plurality of fan blades extending out from the wheel hub sleeve on the rotor; the wheel hub adopts a hollow structure; the wheel hub comprises a shell and a cavity; an annular airbag is arranged on the inner wall, near the rotor side, of the cavity; the annular airbag is filled with table vinegar; the table vinegar is boiled to produce gas to expand the annular airbag; one ends of the fan blades are fixedly connected with the annular airbag; through slots for the fan blades to run through are formed in the shell; the other ends of the fan blades run through the through slots and extend out; serrated grooves are formed in the edges of the fan blades; shrinking grooves are formed in the shell on the two sides of the through slots; conical baffle plates extending out towards the through slots and capable of being clamped into the serrated grooves to fix the fan blades are arranged inside the shrinking grooves; the conical baffle plates can be shrunk into the shrinking grooves. The device can solve the problem that the heat-dissipating device of the switching power module in the prior art cannot adjust the air volume according to the temperature rise change.