A central tube assembly for a filter cartridge and a manufacturing method for the central tube assembly are provided. The central tube assembly includes a first half-tube defines a first flow passage, and having a first water inlet at an end thereof and a water output hole in a side wall thereof, a filtering membrane bent to form a first membrane layer and a second membrane layer, the first half-tube being disposed between the first membrane layer and the second membrane layer; an input-water filtering net connected to the first half-tube and disposed between the first membrane layer and the second membrane layer, a second half-tube disposed outside of a bending of the filtering membrane, defining a second flow passage, and having a water input hole in a side wall thereof and a first water outlet at an end thereof, and a produced-water filtering net.