Abstract: The pressure sensitive characteristic of fiber Bragg gratings is analyzed,the pressure experiments are carried out on different diaphragms.The experimental results indicate that the pressure sensitivity coefficient of fiber Bragg gratings in the FBC20WB2 type diaphragm is much bigger than that in the ZXYC01 type diaphragm.The values are about 376pm/MPa and 45pm/MPa,with measurement precision of 1%(full scale) and 0.5%(full scale) respectively.At the same time there is a very good linearity and repetition between the center wavelength of fiber Bragg grating and pressure change in two diaphragms,and there is scarcely hysteresis effect,their pertinence coefficient is more than 0.9998.The study indicates that the different diaphragm has a great impact on the pressure sensitivity coefficient.