The invention discloses a manufacturing method for a water-resistant bamboo-wood composite board, and belongs to the technical field of building materials. The manufacturing method comprises the following steps of: putting a wood board into mixed enzyme liquid to soak, and taking out the wood board to obtain pre-treated wood board; dropwise adding octenyl succinic anhydride into chitosan liquid, stirring and reacting to obtain primary mixed liquor, dropwise adding a sodium hydroxide solution into the primary mixed liquor to regulate the pH value, heating, stirring and reacting to obtain secondary mixed liquor, dropwise adding hydrochloric acid into the secondary mixed liquor, regulating the pH value of the secondary mixed liquor to obtain modified treatment liquor; putting a bamboo split into the modified treatment liquor to soak, taking out the bamboo split to obtain pretreated bamboo split; stirring and mixing phenolic resin, zinc polyacrylate resin, a coupling agent, nano carbon black, hexamethylene tetramine and graphene oxide to obtain a composite adhesive; and assembling the pre-treated bamboo split, the composite adhesive, the pre-treated wood board, the composite adhesive and the pre-treated bamboo slit, hot-pressing and cooling to obtain the water-resistant bamboo-wood composite board. The water-resistant bamboo-wood composite board prepared by the technical scheme hasexcellent water resistance.