To solve helical non-circular gears manufacturing problem, the simplest mathematical model for hobbing helical non-circular gear and simultaneous-control structure which the machine tool should have were researchedbeen researched. By comprehensive using of helical teeth meshing principles and helical tooling rack generation method, the simplest mathematical model for hobbing helical non-circular gear was deduced. The structure was a 4-axes simultaneous-control structure. Then, by applying the electronic-gear circuit module and electronic differential combination circuit module developed by the authors, simultaneous-control structure of CNC system which hobbing helical non-circular gear required was designed. Based on this, hobbing helical non-circular gears can be achieved, and helical non-circular gears manufacturing problem can be solved.