The effects of using overall affix and two-spot affix between the FBG and underlay on the characteristics of the pressure sensors are compared both experimentally and theoretically.It is found that overall affix can produce large nonlinear effect on the characteristics of output of the sensors.The nonlinear effect caused by the expanded spectral width mainly due to the stress birefringence and the stress grads etc.The experimental result shows that the spectral width caused by using overall affix is 0.28 nm and the linearity can have up to 1.89% of increasing by using two-spot affix.The method of two-spot affix can improve response characteristics of the sensor which is benefit to achieve wavelength demodulation and to improve measurement precision. The effects of using overall affix and two-spot affix between the pressure gg and underlay on the characteristics of the pressure sensors are compared both experimentally and theoretically. It is found that overall affix can produce large nonlinear effect on the characteristics of output of the sensors. The nonlinear effect caused by the expanded spectral width mainly due to the stress birefringence and the stress grads etc. The experimental result shows that the spectral width caused by using overall affix is ​​0.28 nm and the linearity can have up to 1.89% of increasing by using two-spot affix. The method of two-spot affix can improve response characteristics of the sensor which is benefit to achieve wavelength demodulation and to improve measurement precision.