Abstract: The decontamination of the dissolution tank from spent fuel reprocessing outline device is studied, by using FL-AP decontamination agent. The decontamination factor per step is 2.2，2.4, respectively for α, β activities. After dissecting the tank, residual contamination in inner surface of the tank was found to be nonuniform. The exact original contamination value of the tank surface could be approximated by calculating the total amounts of radionuclide distributed on the hanging specimens, the dissecting specimen, and radioactive level in waste decontamination agent. Therefore, it can be concluded that the hanging specimens method is feasible for measuring the decontamination factor of spent fuel dissolution tank.