Objective To evaluate uncertainty of measurement results by analyzing the uncertainty components in the experiment. Methods The lead in rice was determined by graphite furnace atomic absorption according to GB/T5009.12-2010. The mathematical model was established according to JJF 1059.1-2012 to evaluate each uncertainty component. Results By the calculation of each uncertainty component, it was concluded that eventually extended uncertainty was 0.030mg/kg (including factor k=2), the report result was (0.70±0.030) mg/kg. Conclusion The uncertainty were mainly influenced by uncertainties in the introduction of repeatability and fitting curve