A kind of optical fiber MEMS pressure sensor was manufactured by micro electro mechanical systems technology according to the principle of Fabry-Perot cavity interference. A sensitive film which is 6 μm in thickness and 0.502 μm/MPa in mechanical sensitivity was fabricated by adopting the deep boron-diffusion self-stopped etching and magnetron sputtering technique. Based on the intensity-demodulation technology, this kind of pressure sensor makes use of the relation between reflected power and pressure to demodulate the pressure. The study explores the impact of the change of cavity length on reflectance, identifies the light wavelength of linear working point of the pressure sensor, and establishes a stable testing system of fiber Fabry-Perot pressure sensor. The test results show that this kind of sensor has a minimum pressure resolution of 62 Pa and a sensitivity of 0.51 nW/KPa, displaying good linearity, high sensitivity and remarkable repeatability. It can be used to measure the pressure in the human body and the power of the oral denture on the below structure.