A quasi-distributed fiber Bragg grating(FBG) sensing system based on linear by chirped grating is proposed in this paper,aiming at improving the application range of fiber Bragg grating.The characteristics of chirped grating are analyzed using waveguide theory,the reflection spectrum model and the wavelength dependence of the phase group-delay of chirped grating are derived by means of transfer matrix method,and the phase delay curve is obtained.The experimental results show that the strain meas...