Vibration has a great impact on the accuracy of both instruments and machine tools, and its accurate detection and analysis is a prerequisite for effective vibration control. In this study, a high sensitivity and low coupling 3D elastic mechanism, and its parameter optimization method are proposed. The configuration of the 3D elastic mechanism is introduced, and the design of the 3D elastic mechanism is completed through theoretical modeling, parameter optimization, and simulation analysis. Finally, the elastic mechanism is combined with a high-sensitivity and low-coupling sensing system to develop a 3D low-frequency accelerometer system with high performance, and the performance of the accelerometer are tested through experiments. According to the experimental results, the sensitivity of the 3D accelerometer using this elastic mechanism is better than 2. 0 V/ (m·s -2 ), the coupling error is lower than 1. 5% , as well as the frequency response range is 1 ~ 13 Hz, which is in accordance with the design requirements. Therefore, the 3D elastic mechanism proposed in this study is characterized by 3D equal sensitivity and low coupling, and can be widely used in various 3D accelerometers.