Abstract: On the basis of ensuring high purification efficiency of ruthenium in the Purex process,the decontamination efficiency of zirconium should be improved as much as possible to optimize the decontamination process of the Purex process.In this paper,a bench test platform was built to simulate the decontamination process of the Purex process by multi-stage extraction.The effects of IAF acidity and IAS acidity on the distribution of uranium,zirconium and ruthenium in the process and the decontamination effect of zirconium and ruthenium were studied.The results indicate that increasing the acidity of IAF is not conducive to the decontamination of zirconium,but is beneficial to the decontamination of ruthenium,and increasing the acidity of IAs can strengthen the washing of zirconium and ruthenium,which is beneficial to the decontamination of zirconium and ruthenium.At 30℃,when 1 AF was fed with 3.5 mol/l nitric acid and IAS was scrubbing with 3 mol/L nitric acid in the 1 A mixer-settler,the recovery of uranium reached 99.9 %,the decontamination coefficient of zirconium reached 30.38,and that of ruthenium reached 8.69.