For the space scanning optical fiber Fabry- Perot (F- P) sensor demodulation system, the nonlinear distortion of CCD and its influence on absolute phase demodulation are investigated. The CCD response characteristic is measured and a fitting model is built. Then, the influence of nonlinear distortion under different standard deviation of noise is simulated. The simulation results show that the standard deviation of the demodulated absolute phase increases with the increase of the nonlinear distortion rate. Meanwhile, interference order jump error resulting from the nonlinear distortion rate decreases with the increase of noise. The influence of nonlinear distortion is studied based on the optical fiber F-P pressure sensor demodulation system. The experimental results show that the nonlinear distortion rate under a fixed pressure increases with the optical power, and the interference order jump error appears when the nonlinear distortion rate is larger than 26.3%, which agrees with the simulation results. In addition, the demodulation accuracy decreases with the increase of the nonlinear distortion rate when the nonlinear distortion rate of fiber F-P full pressure sensing demodulation ranges from 0.3% to 22.3%. The demodulation error is 0.215 kPa when the nonlinear distortion rate is 22.3% , which has increased by 1.24 times as compared with that when the nonlinear distortion rate is 0.3%. In order to ensure the demodulation accuracy better than 0.04% in full scale, the nonlinear distortion rate should be controlled less than 6.7%.