The invention discloses a method for recovering valuable metal from a waste nickel-zinc battery. The method comprises the following steps: arranging the waste nickel-zinc battery into saturated salt water, and carrying out self-discharge treatment; crushing and screening the nickel-zinc battery subjected to self-discharging treatment to obtain oversize products and undersize products; carrying out magnetic separation on the oversize products to obtain iron residues and nonmagnetic substances; mixing the nonmagnetic substances with the undersize products, then leaching the mixture by sulfuric acid, and filtering to obtain leachate; treating the leachate by a chemical method, carrying out extraction separation to obtain binary mixed liquid of nickel sulfate and cobalt sulfate, zinc salt solution and calcium chloride solution, or binary mixed liquid of nickel sulfate and cobalt sulfate, zinc salt solution, copper salt solution and calcium chloride solution; respectively concentrating and crystallizing the obtained solution, and carrying out centrifugal separation the solution to complete the recovery of the valuable metal. According to the method, secondary pollution to the environment is avoided, the technological process is short, the resource recovery and utilization rate is high, the technical product selection flexibility is high, the cost is low and economical benefits are relatively high.