A filter assembly for a fluid filter comprising: a plurality of filter units assembled in series, and each of the filter units comprising: a connecting member 10 including a connecting disc 11, a connecting pipe 12 which protrudes from a top surface 111 of the connecting disc 11 and is provided with a guiding passage 121 penetrating through the connecting disc 11, and an connecting ring 13 which protrudes from a bottom surface 112 of the connecting disc wherein the filter unit further comprises an input member 20 including an input plate 21, an input ring 22 which protrudes from a top surface of the input plate 21 and fixed to the connecting ring 13, an extending pipe 23 which penetrates through the input plate 21 and is provided for insertion of a connecting pipe 12 of another filter unit in order to connect the extending pipe 23 and the connecting pipe 12 of the connecting member 10 of another filter unit, a plurality of input pipes 24 which protrude from a bottom surface 212 of the input plate 21 and are each provided with an input passage 241 penetrating through the input plate 21, and a separating portion 25 which is disposed in each of the input pipes 24 to divide the input passage 241 into an upper input chamber 2411 and a lower input chamber 2412, each of the separating portions 25 including an input hole 251 in communication with the upper and lower input chambers 2411, 2412; and an output member 30 being fixed on the top surface of the input plate 21, and including an inserting hole 31 for insertion of the extending pipe 23, and a plurality of output protrusions 32 to seal the upper input chambers 2411, and each of the output protrusions 32 including an output hole in communication with a corresponding one of the upper input chambers 2411. a connecting member 10 including a connecting disc 11, a connecting pipe 12 which protrudes from a top surface 111 of the connecting disc 11 and is provided with a guiding passage 121 penetrating through the connecting disc 11, and an connecting ring 13 which protrudes from a bottom surface 112 of the connecting disc wherein the filter unit further comprises an input member 20 including an input plate 21, an input ring 22 which protrudes from a top surface of the input plate 21 and fixed to the connecting ring 13, an extending pipe 23 which penetrates through the input plate 21 and is provided for insertion of a connecting pipe 12 of another filter unit in order to connect the extending pipe 23 and the connecting pipe 12 of the connecting member 10 of another filter unit, a plurality of input pipes 24 which protrude from a bottom surface 212 of the input plate 21 and are each provided with an input passage 241 penetrating through the input plate 21, and a separating portion 25 which is disposed in each of the input pipes 24 to divide the input passage 241 into an upper input chamber 2411 and a lower input chamber 2412, each of the separating portions 25 including an input hole 251 in communication with the upper and lower input chambers 2411, 2412; and an output member 30 being fixed on the top surface of the input plate 21, and including an inserting hole 31 for insertion of the extending pipe 23, and a plurality of output protrusions 32 to seal the upper input chambers 2411, and each of the output protrusions 32 including an output hole in communication with a corresponding one of the upper input chambers 2411.