In order to meet the requirements of vibration monitoring of large mechanical equipment, the authors design a novel three-dimensional (3D) high-frequency fiber Bragg grating (FBG) accelerometer. First, the operation principle of the sensor is introduced; the theoretical calculation and finite element analysis are performed about its structural parameters in this paper. Second, an FBG demodulation method for vibration signal is studied and a compensation method is put forward to measure the error caused by fluctuation of the light source and line loss. Finally, sensing properties such as amplitude frequency characteristics, sensitivity of the sensor, crosstalk coefficient, space acceleration measurement are tested, and the compensation method for measurement error is validated. The results show that the operating frequency bandwidth of the transducer is 10500 Hz, sensitivity is about 1400 mv/g, crosstalk coefficient is larger than 20.6 dB, and the maximum measurement error of space acceleration is 4.8%, the compensation error is less than 5%. Hence, the sensor is used to monitor the vibration state of mechanical equipment.