Abstract: The present utility model discloses a water purifier filter cartridge of simple structure, comprising a filter cartridge cylinder, wherein a central tube coaxial with the filter cartridge cylinder is disposed in the filter cartridge cylinder; a first cavity is formed in the central tube; a filter cartridge body is disposed outside the central tube; the filter cartridge body comprises an RO membrane and a pre-filtering membrane; the RO membrane is wound around the central tube; several water holes communicating the first cavity with the RO membrane are formed in the side wall of the central tube; the pre-filtering membrane is wound outside the RO membrane; a second cavity is formed between the pre-filtering membrane and the filter cartridge cylinder; a first water gap, a second water gap and a third water gap are formed in the top of the filter cartridge cylinder; the first water gap communicates with the first cavity; and the second water gap communicates with the second cavity.