Large railway flatcar body

The utility model discloses a large railway flatcar body which comprises a frame structure and a floor (7). The frame structure is composed of a side beam (1), an end beam (2), a middle beam (3), a sleeper beam (4), a big beam (5) and a small beam (6). The middle beam is formed by welding left joist steel (3a), right joist steel (3a), an upper cover plate (3b) and a lower cover plate (3c), wherein the left joist steel (3a) and the right joist steel (3a) which are arranged at intervals belong to the same type, and are connected through the upper cover plate (3b) and the lower cover plate (3c). The end beam is a cold-formed channel and is connected with the middle beam in a lap joint mode. The side beam is made of the joist steel sharing the same type with the middle beam and is connected with the end beam in a lap joint mode. The left end and the right end of the upper cover plate extend outwards, and are connected with the side beam in a lap joint mode. The sleeper beam is of a variable cross-section box type