The invention discloses a separation and crushing device of downhole pulverized coals of coalbed methane and a method thereof. The settling separation, the crushing and the filtration are performed for the pulverized coals, so that the particle size of the pulverized coals entering a screw pump reaches a normal working range of the screw pump, the accidents of pump blockage, blockage and abrasion caused by the pulverized coals with larger particles entering the screw pump can be effectively prevented, the pump detecting period is prolonged, the development cost of the coalbed methane is reduced, and the blockage of holes of a coalbed methane well by the pulverized coals is prevented; and the device has the advantages of simple structure, convenience for use and high efficiency.