The uncertainty of the determination of lead content in rice by graphite furnace atomic absorption spectrometry (GF-AAS) was evaluated. The main effecting factors on the uncertainty were analyzed. The mathematic model was built according to GB5009.12-2010，based on Guide to Evaluation of the Uncertainty in Chemical Analysis. The result showed that when the lead content in rice was 0.100 ㎎/㎏，the expanded uncertainty was 0.009 ㎎/㎏(k=2). When determining the lead content in rice by GF-AAS，the most influential factor on the total uncertainty was the uncertainty produced during sample digestion process and determining the mass concentration of lead in sample digestion solution.