It requires high security for useing silane decomposition reaction to produce the polycrystalline silicon. For this reason, the paper introduces the central facilities of the polycrystalline silicon production, and bases on production process, to devise a control system which combines PLC and industrial ethernet technology. The system controls temperature and pressure of the decomposition furnace, cooling water system, and production process. The practical result showes that the system is reliable and steady. It meets the requirements of process.