The dynamic mechanical-electric coupled finite element models of a piezoelectric balance is built as SOLID5 (piezoelectric couple element type) and SOLID45 (3-D structural element type) by ANSYS software. In the simulating process of calibration of the piezoelectric balance, the first six natural frequencies and mode shapes were calculated by the element modal analysis. And the static analysis of the piezoelectric balance was developed under three loads, which includes axial force, yaw force and pitch force. To analyze the influence of other components by principal components, the output voltages of all twelve piezoelectric pieces were observed. Furthermore, we changed thickness of the piezoelectric pieces, and investigated the relationship between piezoelectric pieces thickness and output voltages. Finally, to reduce the impact on other components of the principal components and to improve the calibration accuracy, the piezoelectric balance can be optimized by modifying all kinds of parameters of the piezoelectric balance.