The utility model relates to a grading wheel assembly of ultrafine disintegrator, which comprises a chassis 1, a blade 2, a ring disc 3 and a collar 4. The peripheral edges of the chassis 1 and the ring disc 3 are radically provided with several blade slots 11, 31 corresponding to the chassis 1 and the ring disc 3. Both ends of the blade 2 are axially inserted into the slots 11, 31 which are corresponding to the chassis 1 and the ring disc 3. The outer surroundings of the ring disc 3 are sheathed by the collar 4. The utility model has the advantages of convenient dismounting and cleaning, fine classifying fineness and good classifying effect.