In this paper, proportional and integral (PI) pitch controller is analyzed and designed for a large wind turbine generator (WTG) by using graphical approach. Firstly, the transfer function of the wind turbine which including a time delay in the hydraulic pressure driven unit of pitch control system is derived. The complete stabilizing set in the plain of proportional–integral gains can then be drawn and identified immediately based on the presented method, rather than computed mathematically. The influence of the time delay in hydraulic pressure driven of pitch unit on the stability region of PI controller is analyzed as well. Finally, the proposed techniques are verified by using simulation results to the actual model of WTG.