In the end, the demodulation method of Fabry-Perot sensors ultimately serves for practical application. The complex environment in engineering applications affects the performance of the Fabry-Perot sensors. So, the research on the demodulation method should not be limited to the laboratory environment. Developing a demodulation method with engineering application value is vital.Fiber optic Fabry-Perot sensors have attracted a lot of attention in many fields such as medical detection, underwater acoustic detection, and electric power monitoring due to their high sensitivity and strong anti-interference ability. The parameters of the light source, the structure of the sensing head, and the demodulation methods are the main factors that restrict the detection ability of fiber optic Fabry-Perot sensors. Demodulating the fiber optic Fabry-Perot sensors is to extract cavity length from the output optical signal which indicates the information of vibration, displacement, acceleration, temperature, and other parameters sensed by the sensor's head. An excellent demodulation method can improve the demodulation speed, resolution, and dynamic range of the fiber optic Fabry-Perot sensor. However, there are dozens of demodulation methods for the fiber optic Fabry-Perot sensor, and it is difficult to choose the appropriate demodulation method for specific application scenarios. In this paper, firstly, the characteristics of the signal output from the optical fiber Fabry-Perot sensor are reviewed. Then, the influencing factors of the common demodulation methods are described in detail, and the improvement methods proposed by domestic and foreign research institutes are also introduced. Finally, the choice principle of the demodulation is proposed from two aspects: the applicable condition and the multiplexing of the optical fiber Fabry-Perot sensor.