The invention belongs to the technical field of hydrometallurgy, and relates to a preparation method and application of battery grade manganese sulfate. The preparation method of the battery grade manganese sulfate comprises the following steps of: (A) precipitating copper ion, calcium ion and zinc ion in a copper chloride manganese solution to obtain first filtrate; (B) in a protective atmosphere, mixing the first filtrate, a precipitating manganese agent and a base solution for manganese precipitation reaction and separation of solid and liquid to obtain manganese hydroxide; (C) mixing themanganese hydroxide with concentrated sulfuric acid for neutral reaction to obtain coarse manganese sulfate, and refining the coarse manganese sulfate to obtain the battery grade manganese sulfate; wherein in step (B), the precipitating manganese agent comprises ammonia water; and the base solution comprises the ammonia water and soluble hydroxide. The preparation method of the battery grade manganese sulfate can not only achieve preparation of the battery grade manganese sulfate, but also benefit recovery of zinc, copper, calcium and the like, thereby maximizing utilization of copper-manganese chloride waste liquor, reducing cost and conforming to a concept of sustainable development.