The invention provides a grain unloading machine special for a barn. The grain unloading machine comprises a head box body, the head box body is fixedly mounted on a support, a drive device is mounted inside the head box body, the drive device is connected with a head wheel assembly, a transition segment is connected to the position behind the head box body, and a multi-section conveying machine shell is connected to the position behind the transition segment; a plurality of feeding devices are mounted on the top of the conveying machine shell in parallel, and sections of the conveying machine shell are connected through a transition connecting device; and a tail transition segment is connected to the tail section of the conveying machine shell, and a tail box body is connected to the position behind the tail transition segment. By means of a grain unloading production line, the technical problems existing in a traditional grain unloading machine are effectively solved, and accordingly the grain unloading efficiency of the barn is improved, the labor intensity of operation workers is reduced, the unloading time is saved, the work efficiency is improved, and the grain unloading machine special for the barn is suitable for work of various bulk grain wharf ship unloaders.