A scheme for stabilizing the Fabry-Perot (FP) cavity based on the Pound-Drever-Hall (PDH) technique is proposed for the need of more stable FP cavity. According to the theoretical calculation model, the static and dynamic response characteristics of the FP cavity resonant optical system are analyzed in details. The error signal obtained by the static analysis can be used to lock the FP cavity, and the frequency response obtained by the dynamic response analysis helps to design a control loop to maintain the FP cavity at the chosen operating point. The numerical simulation results show that when the optical gain is 0.785 W/(°) and the error signal stays at the milliwatt level, the length stability precision of the FP cavity achieves 4 pm. The validity and feasibility of the scheme are verified by comparing the beam spot size and shape of the reflected light before and after the FP cavity locking.