A fiber Bragg grating (FBG) accelerometer based on diaphragm and diamond structure is proposed. The acceleration detection mechanism of the sensor is explained, and its sensitivity and resonance frequency expression are derived. The structural parameters of the sensor are optimized by using ANSYS and MATLAB softwares, and the FBG accelerometer with small structural size and meeting the practical application requirements is obtained. The finite element model is constructed to simulate the vibration characteristics of the sensing system. The sensor is fabricated and tested for dynamic and static characteristics. The experiments show that the sensor has better temperature compensation effect under the temperature of 20-90 ℃, which effectively reduces the influence of temperature on acceleration measurement. The first-order natural frequency of the sensor is about 681.4 Hz. In the range of 0-500 Hz, the sensor''s sensitivity has a good linear relationship with the vibration signal frequency. The combined application of the diaphragm and diamond structure enhances the sensor''s ability to resist lateral interference with a lateral interference of less than 5%.