A central tube assembly for a filter cartridge, comprising: a first half-tube having a first fitting surface extending along an axial direction of the first half-tube, and the first fitting surface being slotted to provide a first flow passage extending along an axial direction, the first half-tube having a first end closed and a second end having a first through hole communicated with the first flow passage, a side wall of the first half-tube having a first via hole communicated with the first flow passage; a second half-tube having a second fitting surface extending along an axial direction of the second half-tube, and the second fitting surface being slotted to provide a second flow passage extending along the axial direction, the second half-tube having a first end closed and a second end having a second through hole communicated with the second flow passage, a side wall of second half-tube having a second via hole communicated with the second flow passage, the first half-tube and the second half-tube being butted, the first fitting surface and the second fitting surface being opposite to each other, the first half-tube and the second half-tube being fitted to provide a hollow straight tube; and a membrane element disposed between the first half-tube and the second half-tube, and closing the first flow passage and the second flow passage respectively, wherein two sides of the inner surface of the first flow passage each are provided with a plurality of first transverse reinforcing rib sets, wherein the two sides of the inner surface of the first flow passage are opposite to each other along a direction perpendicular to an axis of the first flow passage, and wherein the plurality of first transverse reinforcing rib sets are staggerly arranged on the two opposite sides of the inner surface of the first flow passage, wherein the inner surface of the first flow passage is provided with an axial reinforcing rib extending along the axial direction of the first half-tube, and the plurality of first transverse reinforcing rib sets are arranged on two sides of the axial reinforcing rib, wherein two sides of the inner surface of the second flow passage each are provided with a plurality of second transverse reinforcing rib sets, wherein the two sides of the inner surface of the second flow passage are opposite to each other along a direction perpendicular to an axis of the second flow passage, and wherein the plurality of second transverse reinforcing rib sets are staggerly arranged on the two opposite sides of the inner surface of the second flow passage, and wherein the plurality of reinforcing ribs (113, 114, 24) are arranged to abut against the membrane element. a first half-tube having a first fitting surface extending along an axial direction of the first half-tube, and the first fitting surface being slotted to provide a first flow passage extending along an axial direction, the first half-tube having a first end closed and a second end having a first through hole communicated with the first flow passage, a side wall of the first half-tube having a first via hole communicated with the first flow passage; a second half-tube having a second fitting surface extending along an axial direction of the second half-tube, and the second fitting surface being slotted to provide a second flow passage extending along the axial direction, the second half-tube having a first end closed and a second end having a second through hole communicated with the second flow passage, a side wall of second half-tube having a second via hole communicated with the second flow passage, the first half-tube and the second half-tube being butted, the first fitting surface and the second fitting surface being opposite to each other, the first half-tube and the second half-tube being fitted to provide a hollow straight tube; and a membrane element disposed between the first half-tube and the second half-tube, and closing the first flow passage and the second flow passage respectively, wherein two sides of the inner surface of the first flow passage each are provided with a plurality of first transverse reinforcing rib sets, wherein the two sides of the inner surface of the first flow passage are opposite to each other along a direction perpendicular to an axis of the first flow passage, and wherein the plurality of first transverse reinforcing rib sets are staggerly arranged on the two opposite sides of the inner surface of the first flow passage, wherein the inner surface of the first flow passage is provided with an axial reinforcing rib extending along the axial direction of the first half-tube, and the plurality of first transverse reinforcing rib sets are arranged on two sides of the axial reinforcing rib, wherein two sides of the inner surface of the second flow passage each are provided with a plurality of second transverse reinforcing rib sets, wherein the two sides of the inner surface of the second flow passage are opposite to each other along a direction perpendicular to an axis of the second flow passage, and wherein the plurality of second transverse reinforcing rib sets are staggerly arranged on the two opposite sides of the inner surface of the second flow passage, and wherein the plurality of reinforcing ribs (113, 114, 24) are arranged to abut against the membrane element.