The invention relates to an automatic dust-removing cotton-assorting device for cotton processing equipment. The device comprises a cotton feeding pipeline component, a cotton assorting box component, a ventilation pipeline component and a draught fan component, wherein the cotton assorting box component is connected with the end part of the cotton feeding pipe component; the ventilation pipeline component is arranged at one side, opposite to the cotton feeding pipeline component, of the cotton assorting box component; the draught fan component is arranged at the end part, opposite to the cotton assorting box component, of the ventilation pipeline component; the cotton feeding pipeline component, the cotton assorting box component, the ventilation pipeline component and the draught fan component are communicated fluidly; the cotton assorting box component comprises two or more cotton assorting boxes; the two or more cotton assorting boxes are controlled to realize that one portion of the two or more cotton assorting boxes alternately perform cotton collection operation and cotton falling operation while the other portion of the two or more cotton assorting boxes alternately perform cotton falling operation and cotton collection operation. The automatic dust-removing cotton-assorting device disclosed by the invention has the advantages of novel flexible air-tight structure, advanced cotton assortment function, reliability in use, lower energy consumption and use cost, high operation efficiency, good dust removal effect, and uniformity and high quality of falling cotton.