A theoretical model of the fiber-optic Fabry-Pérot sensor based on a pressure-sensitive film is developed by carefully analyzing the operation mechanism of the sensor. The total detection sensitivity of the sensor is obtained by multiplying the optical sensitivity proportional to the transfer function of the Fabry-Pérot cavity, and the sound pressure response of the film. The total measurement noise is obtained by taking into account the dark current noise and thermal noise of the photodetector, the relative intensity noise and phase noise of the probe laser. By employing the model, the dependences of the signal-to-noise ratio (SNR) of the Fabry-Pérot sensor on the coating reflectivities, the Fabry-Pérot cavity length, the thickness and effective radius of the pressure-sensitive film are discussed in detail. For the case that the film is made of pure silicon and the probe light is provided by a commercial continuous wave (cw) single frequency fiber laser operating around 1580 nm, the best SNR as high as 104.9 dB can be achieved when the effective radius and thickness of the film are respectively 150 μ m and 1.5 μ m, the reflectivity of the coatings on the fiber end and film are respectively 0.55 and 0.99, as well as the length of the Fabry-Pérot cavity is 14.9 μ m. This SNR is nearly three times higher than the reported Fabry-Pérot sensors operating in either free space or fiber coupled scheme, and consequently meet the demand of the high resolution photoacoustic imaging application. In the future investigations, tunable cw single frequency solid state laser offering better noise properties, and new pressure-sensitive material with higher Young’s modulus are expected to balancethe pressure detection range and further raising up the SNR of the Fabry-Pérot sensor. Our model is still valid in these cases, thus can be used to guide the design and optimization.