In order to measure weak pressure, a novel sensor based on the Stokes p arameter of FBG is proposed in this paper.The evolution of the first normalized Stokes parameter s1with respe ct to pressure is studied theoretically and experimentally.A theoretical model for pressure sensing by us e of the s1is built and numerically simulation is also carried out.The dual-wavelength analytical method is propos ed to reduce the influence of Bragg wavelength drift and improve the measurement accuracy.Under the pressure condit ions of 0－5N, the experimental pressure sensitivity is 0.0754/N.Good agreements between experiment results and numerical simulations verify thefeasibility ofthe method.