The invention discloses a small railway maintenance machine with a shape recognition function. The small railway maintenance machine comprises a tamping and ballast leveling device, a railway shoulder and ballast bed shape correction device, a grab bucket ballast clearing device, a ballast collection and discharge device, a sleeper end ballast clearing device, a sprocket ballast discharge device, a synchronous assembling and disassembling device for four nuts, a first rail lifting device, a shunting and sleeper push-pull device, a sleeper hanging device, an electric generator, a hydraulic system and control system cabinet and a rail car. The small railway maintenance machine has the advantages that working positions can be aligned rapidly; ballast on a ballast bed between sleepers, the outer sides of the sleeper ends and under steel rails can be discharged automatically, sand and soil in the ballast can be separated automatically, the ballast can be backfilled between the replaced sleepers to be tamped and leveled, and the shapes of railway shoulders and the ballast bed are repaired automatically; the four nuts can be assembled and disassembled synchronously, so that the fatigue life of bolts is prolonged, and connecting reliability between the sleepers and the rails is ensured; the shunting and sleeper push-pull device which is an integrated device is compact in structure and adaptive to various sleeper replacement operations in straight and curve rail sections, and accordingly high sleeper replacement efficiency is achieved.