The invention provides a ginned cotton dust collector comprising a first conveying belt and a second conveying belt parallel to the first conveyer belt. The first and second conveyer belts are all in a filter screen structure and rotate in the opposite directions; to-be-processed ginned cotton are conveyed between the first and second conveyer belts and irradiated by microwaves; a first housing is provided with a steam port and a first air pumping port; a second housing is provided with a cold air port and a second air pumping port; and the first and second housings are all fixed on a vibration device. Temperature differences are caused between cotton fibers, cottonseed chips and dust particles in the ginned cotton by the use of cold air and micro waves; the ginned cotton is processed by steam and surfaces of the cottonseed chips and the dust particles are frozen; with action of the vibration device, self gravity of the cottonseed chips and the dust particles are increased due to the ice, so the ginned cotton can be easily tossed out during the vibration; and the cottonseed chips and the dust particles in the ginned cotton can be effectively separated.