Abstract: The sorption of americium (Am) on container wall, which occurred in the through-diffusion cell tests using groundwater and granite from Beishan, Gansu Province, China, was investigated. It is shown from the through-diffusion cell tests that the concentrations of Am in the source reservoirs decrease notably with time increase. The prime one of some possible reasons for this decrease is the sorption of Am on the container wall. The sorption behavior of Am is dominated by its chemical speciation. The chemical speciation of Am often varies with the pH of the solution, which results in that the pH has significant influence on the sorption behavior of Am. The failure of attempts to lower the sorption loss of Am suggests that the through-diffusion cell test is not practicable for strongly sorbed nuclides such as Am.