Abstract: This paper put forward ideal geometry parameters of arch cylindrical gear based on analyzing the geometry parameters and process methods of similar arch cylindrical gears. It analyzed the mesh characteristics of two tooth surfaces of gear pair. By graphical representation of the toothsurface equation and the mesh line expression，it demonstrated the mesh state of two teeth surfaces with graph, which can verify the feasibility of the gear’s geometry parameters. It can be concluded that the radius of concave surface and convex surface of the tooth must be equal in the gear, the tooth thickness is equal to the slot width on the different radial section of the gear teeth and the pressure angle at the reference circle must be equal. Based on it, the processing method of the involute arch cylindrical gear and the parallel rod gear processing device, were put forward.