Abstract: Institute of Materials, China Academy of Engineering Physics, Jiangyou 621907, ChinaAbstract:The characteristic of the ²³⁸Pu/^239,240Pu activity ratio in the soil samples around nuclear facilities can be used to assess the nuclear activities. In order to obtain an accurate isotope ratio, an analytical method for ²³⁸Pu/^239,240Pu activity ratio needs to be established. Based on the analysis procedure of plutonium activity concentration with TOA extraction, this paper was focused on the removal of impure elements such as U, Th and Am by scrubbing with proper amount of nitric acid and hydrochloric acid solutions. A co-precipitation step was introduced to optimize the pretreatment process, and a new procedure for determination of ²³⁸Pu/^239,240Pu activity ratio in soils was developed. For 25 g soil sample, the chemical recovery of Pu of the procedure is greater than 70%, and the decontamination factors of U, Th and Am are greater than 10⁴, 10⁴ and 10³, respectively. The minimum detection activity concentrations are found to be (6.0±1.6)×10^-6 Bq/g for ²³⁸Pu and (6.4±0.4)×10^-6 Bq/g(n=3) for ^239,240Pu. This method can be widely applied to the analysis of ²³⁸Pu/^239,240Pu activity ratio in environmental soil samples and thus provide technical support for arms control verification and environmental monitoring.