Abstract: A novel optical fiber pressure sensor based on Fabry-Perot（FP） interferometer and phase demodulation method is described.MEMS techniques and the common communicational components are used to fabricate the sensor. The principle of pressure measurement has been introduced;the relationship between silicon membrane size and sensor performance has been illuminated by simulation.Phase demodulation method based on Fourier transformation is explored,which can reduce errors resulting from intensity variation of light source.Experimental results demonstrate that a high linear response in the range of 0MPa to 3MPa and a reasonable sensitivity of 3.50 m/MPa（change in cavity/loaded pressure） have been obtained in this sensor.