Through wet process, valuable metals such as nickel, cobalt, manganese, lithium, and by-products such as sodium sulfate and ammonium sulfate in the black powder of ternary batteries and lithium iron phosphate batteries can be recovered efficiently. This process has the advantages of strong material adaptability, high metal recovery, high purity, high quality and stability, low energy consumption and long-term continuous and stable operation. Among them, the process of recycling battery grade iron phosphate products from phosphorous residue is at the leading level in the industry.