The basic functions  of  steam turbine control  system can be summarized as speed control and load control. In the early stage,the speed control system is basically comprehensive hydraulic control. However,it is prone to various speed instability, and loads fluctuation, which affects the production and causes to the potential danger. As the previous control system gradually cannot meet requirements of modern production. Therefore, it is necessary to optimize the steam turbine control system. Our company’s control system mainly adopts Wood Ward 505 control system and we introduce Germany SIEMENS’s technology to produce hydraulic actuators and the mechanical spare parts. After transformation, the operation of the control system is reliable, the speed control device is compact and the maintenance is convenient, and improves the automation . This Modificationalso can solves problems, such as instable adjustment, the fluctuation of loads, the lagging response and the leakage of the oil system and so on. In conclusion ,it is worth implementing.