Abstract: ICP-OES, which is short for inductively coupled plasma optical emission spectrometry, is frequently used to determine Al₂O₃ content in ceramic bonds.To improve the accuracy, comparative tests were implemented to study the causes of uncertainty and evaluate it.The uncertainty caused by test repeatability, solution concentration, liquid volume, dilution degree and sample weighing was assessed.The combined uncertainty and expanded uncertainty was calculated based on an international method.Assessment shows that test repeatability and solution concentration affect the uncertainty most.In conclusion, when determining the content, parallel repetitive measurement should be conducted with special attention paid to solution concentrations when drawing a standard curve.