The fiber Bragg grating(FBG) sensor has extensive application prospects in the field of explosion impact testing for its merits like high sensitivity, wide measurement range, anti-electromagnetic interference capability, high temperature resistance and so on. An anti-impact FBG pressure sensor was designed for the performance requirements of pressure sensor in the process of cavity explosion pressure change. The sensor used a flat diaphragm as the bearing surface, and used the deflection under uniform pressure to stretch the FBG so as to generate displacement. The mechanical model of the sensor was theoretically calculated and the finite element simulation was carried out. Result shows that the error between theoretical analysis and numerical simulation is less than 2%. And the sensor was calibrated using a standard pressure source with a final pressure sensitivity of 545.187 kPa/nm and a linearity correlation of 99.998%. In addition,according to the protection requirements of the cavity explosion site, an effective anti-explosion protection device was designed, and the sensor was successfully used for the measurement of gas pressure change history after cavity explosion, which achieved good test results.