The pressure sensor characteristic of fiber Bragg grating(FBG)was analyzed,the relation between the central wavelength of reflection wave of FBG and pressure was given,and the expression of the pressure sensitivity coefficient was also given. The pressure experiments were carried out on the plat diaphragm,whose type was ZXYC01,which was self-designed.The experimental results indicated that the pressure sensitivity coefficient of fiber Bragg grat-ings on the ZXYC01 type diaphragm is about 46 pm/Mpa,its measurement precision is 0.5% F.S. And the theoretical pressure sensitivity coefficient is 51 pm/MPa. The experimental results agree with the theoretical one,and they are 23 and 26 times of that of the bare fiber Bragg grating respectively. At the same time there is a very good linearity and repetition between the center wavelength of fiber Bragg grating and pressure change on the diaphragm,and there is scarcely hysteresis effect.