The invention provides a medicine bag hanging device for an aquaculture net cage and an application method, and belongs to the field of aquaculture net cage small breeding equipment. The medicine bag hanging device comprises a cylindrical structure with holes and a top cover. Three supporting sticks connected with the cylinder wall are arranged at the opening portion of the cylindrical structure and parallel to the bottom face of the cylindrical structure, triangular prism bodies are connected between the supporting sticks and the bottom face of the cylindrical structure, the upper ends of the triangular prism bodies are fixed to the supporting sticks, the lower ends of the triangular prism bodies are fixed to the bottom face of the cylindrical structure, sunken tightening ring grooves are formed in the upper portion and the bottom of the outer wall of the cylindrical structure, and a handle is arranged on the top cover. Quicklime powder and zeolite powder are evenly mixed according to the 3:1 weight ratio and then added to a drum, the top cover is screwed up, and the medicine bag hanging device is hung on the outer side of netting of the aquaculture net cage in the water flow direction for disinfection. The medicine bag hanging device is simple in structure and convenient to operate, the quicklime powder can be bagged in water and is not hardened, the medicine effect is slowly released, and the disinfection effect of quicklime bagging of the aquaculture net cage is effectively improved.