The variable pitch control system of tidal current turbines is one of the key components for the commercial application of tidal current energy. Based on the analysis of the tidal current pitch control system's characteristics， a novel hydraulic pitch control system has been designed. The system consists of a rack-and-pinion actuator mechanism with a front-located hydraulic cylinder， and an electro-hydraulic proportional control subsystem which is designed using discretization method. A prototype system has been built and tested in a workshop. Test results show that the pitch adjustment range of the designed system is 188.3° with a maximal pitching speed of 3.36°/s， which validates the bidirectional running function of the system. In addition， it is found that the pitch control system with a numerical PID algorithm has fast response and provides precise control of the pitch angle. The step response adjustment time and steady-state error of the system is less than 1 s and 0.05° respectively.