The invention discloses a butterfly valve type flap valve for a two-way flow channel and an application method of the butterfly valve type flap valve. The butterfly valve type flap valve comprises a first baffle and a second baffle, a flap valve shaft for fixing the flap valve and the two-way flow channel, wherein the first baffle and the second baffle are composed of an upper small baffle and a lower small baffle; the first baffle and the second baffle are clamped in baffle grooves, the positions of the first baffle and the second baffle are controlled through a hoist to realize the change ofthe form of the flapper valve; and a gasket strip is arranged at the interface of the flap valve and the upper baffle and lower baffle, the impact force between the flap valve and the baffles can bereduced, and the service life of the flap valve and the baffles can be prolonged. When the two-way flow channel acts as a water outlet channel, the butterfly valve type flap valve is opened in the forward direction and is automatically closed in the reverse direction; and when the two-way flow channel acts as a water inlet channel, the butterfly valve type flap valve is opened in the reverse direction and is automatically closed in the forward direction. Compared with a traditional flap valve, the application field of the butterfly valve type flap valve for the two-way flow channel and the application method of the butterfly valve type flap valve are more extensive.