Abstract: A complete uncertainty estimation process for balance calibration is established:as-sessing the calibration system uncertainty,assessing the bias limit and precision limit based on checking load residuals to estimate the uncertainty from other errors,and combining them to ob-tain the total uncertainty result.For the BCS-100 calibration system,balance TG624C is calibra-ted seven times repeatedly to implement the method.The result shows that:(1 )The uncertainty caused by the roll angle of balance installation and the angular displacement of balance in the cali-bration are the main components,which shows the direction to upgrade the calibration system;(2)Due to the interference ofY and Mz,the uncertainties of Q、Z and My are larger;(3)The pre-cision limit is much smaller compared to the bias limit.The method is also applicable to other calibration systems.