The invention discloses a mechanical arc-shaped workpiece polishing machine, and belongs to the technical field of mechanical part machining. The mechanical arc-shaped workpiece polishing machine comprises a workbench, a positioning mechanism, a driving box, an adjusting box and a polishing assembly. An arc-shaped workpiece is placed on one of positioning blocks, a positioning plate is moved through a driving mechanism, the arc-shaped workpiece sequentially passes through a middle pressing block, a side pressing blocks and a middle pressing block, which are in three fixing states, in the moving process to make the arc-shaped workpiece always kept in a fixed state in the polishing process, a curve guide rail of a lifting guide rail in an adjusting mechanism is consistent with the arc-shapedworkpiece in shape in the polishing process, a moving plate drives the lifting guide rail to move through a rotating second gear in order to make a polishing roller move relative to the curve guide rail, after the workpiece on one side is polished, a workpiece to be machined is placed, the other workpiece at the other side is polished according to the same principle, after the two workpieces areprocessed, the positioning plate returns to the initial position, the above processes are repeated to polish two workpieces.