The invention provides a waste lithium ion battery processing method. The waste lithium ion battery processing method comprises S1, crushing battery cells to obtain crushed battery cells and volatileorganics; S2, performing low-temperature gasification and pyrolysis on the crushed battery cells to obtain pyrolysis gas and solid residues; S3, burning the pyrolysis gas and the volatile organics toobtain flue gas; S4 spraying lime milk into the flue gas for deacidification reaction to convert phosphorous acid gas inside the flue gas into calcium phosphate and fluorous acid gas into calcium fluoride; dedusting and then emitting the reacted flue gas; S5, fine-crushing and screening the solid residues to obtain powder and metal pieces; S6, recycling iron, aluminum and copper in the metal pieces; S7, acid-leaching and then filtering the powder to obtain filter liquor, and preparing precursor materials with the filter liquor. The waste lithium ion battery processing method provides a complete waste lithium ion battery processing route to recycle metal resources and meanwhile to perform harmless treatment on the organics and hazardous materials, thereby being a recycling, green and environment-friendly processing process.