Abstract: Cadmium oxide is used as the raw material of the certified reference material and is prepared to cadmium standard solution with concentration of 1000 μg/mL. The homogeneity, stability and certified value of the solution are tested by inductively coupled plasmamass spectrometry. The sources of uncertainty produced in analysis process were discussed and the uncertainty of Cd standard solution was assessed. The expanded uncertainty was obtained from combined standard uncertainty multiplied by expanded factor of 2 under the confidence level of 95% and the experimental data also shows that stable period of Cd standard solution is two years.