The invention discloses a preparation method of a nanostructured high-temperature lubricating composite coating. The preparation method comprises the following steps: weighing NiCrAlY, Mo and Ag powder in parts by mass, then mixing the powder, adding methanol and introducing nitrogen gas for sealing, performing ball milling to prepare mixed powder; adding deionized water to the mixed powder afterball milling to prepare a suspension liquid, and then performing spraying granulation to prepare nanostructured spraying powder; cutting a substrate material bar into samples, polishing surfaces of the samples, then ultrasonically cleaning, performing sand blasting treatment on the ultrasonically cleaned samples, and ultrasonically cleaning again after the sand blasting treatment; performing preheating treatment on the ultrasonically cleaned samples, and then performing spraying treatment on the preheated samples by adopting a plasma spraying method with the prepared spraying powder; and performing thermal treatment on the sprayed samples, and then cooling with a furnace to prepare a NiCrAlY-Mo-Ag composite coating. The preparation method disclosed by the invention effectively improves anorganizational structure of the composite coating, and improves the mechanical properties and the tribological properties in a wide temperature range of the composite coating.