Abstract: As a nuclide with multi valence and high fission yield, ⁹⁹Tc has special extraction behavior and redox characteristics in PUREX process, and is needed to control its trend in the reprocessing process of the spent fuel in the power reactor. In this paper, the basic chemical properties of technetium is firstly described and the distribution behavior of technetium in the uranium-plutonium co-decontamination stage, technetium-scrubbing stage and uranium-plutonium separation stage of PUREX process is mainly focused on. Then the influence of acidity, ion concentration and reductive stripping system on the trend of technetium are analyzed, which can provide reference for further controlling its trend and separation in the future.