The invention discloses a preparation method of a double-layer ribbed bi-color reinforced composite pipe. Plastic ribbed special-shaped strips are extruded through a first extruding machine and a second extruding machine together, then the strips are wound through a molding roller, then molten plastisol is extruded into the strips through a third extruding machine and a fourth extruding machine, and the double-layer ribbed bi-color reinforced composite pipe is obtained through extrusion. The double-layer ribbed bi-color reinforced composite pipe is of a double-layer bi-color structure, so that the double-layer ribbed bi-color reinforced composite pipe is more attractive, and the characteristic of conveniently recognizing the product is achieved at the same time; and meanwhile, ribs corresponding to hollow cavities in the two sides of a wave trough can improve the ring flexibility and ring stiffness of the pipe.