A new fiber-optic pressure sensor is studied. A nonlinear compensation method for optical fiber micro bend sensor by using strain nonlinear characteristics of trapezoidal springs and a way to overcome the instability of optical path loss by using differential detection are proposed. The principles of the fiber microbend sensor with trapezoidal spring are introduced. Response curve of trapezoidal spring deformation at pressure of the aerodrome is nonlinear fitted, and the square curve is achieved. Atmospheric pressure from 0 to 0.1 MPa is experimentally tested to verify sensing characteristics. Results show that output voltages and gas pressures have good linearity in the fiber-optic pressure sensors，and pressure measurement sensitivity coefficient is about 2000 mV/MPa. It can meet the requirements of pressure measurement in monitoring of meteorology and aircraft height.