The invention relates to a nano-composite air electrode catalyst for a zinc-air battery and a preparation method of the nano-composite catalyst, belonging to the technical field of zinc-air batteries. The nano-composite catalyst is composed of manganese dioxide, nano-silver, a carbon nano tube and a carbon material in the mass ratio of (0-0.5) to (0-0.5) to 1 to (1.75-2.75), wherein the mass of manganese dioxide and the mass of nano-silver cannot be zero at the same time. Due to the addition of nanometer materials such as nano-silver and the carbon nano tube, the wettability of the nano-composite catalyst is improved, and the reduction reaction of oxygen in a three-phase boundary formed by electrolyte, catalyst material and oxygen is facilitated; meanwhile, the composite catalyst formed by manganese dioxide and nano-silver has oxygen reduction effect higher than that of a single catalyst. The nano-composite catalyst adopts the preparation technology comprising the steps of pretreatment, granulation, ultrasonic dispersion and ball-milling treatment, the operation is simple and efficient, and the application prospect is good.