The invention discloses a device for cleaning bored pile steel protective case inner wall mud and an application method thereof. The device comprises an inner barrel, an outer barrel and a pneumatic capsule, wherein the inner barrel and the outer barrel are both in circular shapes, the inner barrel is located in the outer barrel, the circle centers of the inner barrel and the outer barrel coincide, a concrete-filled cavity is arranged between the inner barrel and the outer barrel, and the concrete-filled cavity is filled with concrete. The pneumatic capsule is in a ring shape and is blanketed on the outer barrel. A plurality of arc-shaped steel plates are arranged outside the pneumatic capsule, and all the arc-shaped steel plates are evenly distributed along the circumference direction. The device for cleaning the bored pile steel protective case inner wall mud and the application method thereof are simple in structure, easy in spot operation and capable of being reused. The cleaning effect of the bored pile steel protective case inner wall mud can be improved greatly, the effective bonding of the steel protective case and the pile foundation concrete is further guaranteed, the development of the mechanical property of the steel protective case is improved, and the reinforcement ratio of the pile foundation or the pile diameter can be reduced.