The invention discloses a grain screening device. The grain screening device comprises a screening tank which is obliquely arranged; a discharging opening is formed in the lower side of the screeningtank, a frame is arranged in the screening tank, and the frame is not in contact with the screening tank; a screening net is arranged at the bottom end of the frame and arranged at the position 100-200 mm from the inner bottom face of the screening tank, two first inserting rods are arranged on one side of the frame, and each first inserting rod penetrates through the screening tank and extends tothe exterior of the screening tank; two second inserting rods are arranged on the other side of the frame, each first inserting rod is arranged corresponding to the corresponding second inserting rod, and each second inserting rod penetrates through the screening tank and extends to the exterior of the screening tank; and springs are connected with the second inserting rods in a sleeving mode andslidably connected with the second inserting rods, and the springs are arranged between the screening tank and the frame. The grain screening device has the advantages that by means of the grain screening device, the grain husk and a large amount of broken straws from the grain collected by a harvester can be removed, and the automatic screening of the grain is achieved through motors and cams.