Abstract: The PandaX experiment uses a two-phase liquid xenon detector to directly detect dark matter.According to the sensitivity requirements of the dark matter detector,the content of radioactive krypton-85 and radon-222 in the liquid xenon need to be reduced to obtain high-purity xenon.The PandaX-4T team developed and designed an efficient cryogenic distillation system through the McCabe-Thiele(M-T)method and the conservations of material and energy.According to the design,this system can reduce the mole fraction of krypton in commercial xenon from 5×10^-7to 1×10^-14 at a feeding mass flow rate of 10 kg/h when the reflux ratio is 145 and the recovery rate is 99%.It can also be operated in the reverse direction through rectification,at that time,when the reflux ratio is 0.16 and the recovery rate is 99%,the radon content in the detector is reduced to 35% of the radon content in original xenon at a feeding mass flow rate of 56.5 kg/h(160SLPM),so as to meet the low background and high sensitivity requirements of the detector.This paper analyzes its gas phase load based on the commissioning and operating data of the distillation system,and uses Hysys software to simu-late,and proposes the optimized operating parameters of the cryogenic distillation operation,the simulation results are basically consistent with the experimental results,which proves that the simulation model is close to the experimental model,and proves the reliability of the simulation method.It plays an important role in improving the product purity of cryogenic distillation system for the removal of krypton and radon by ultra-high purity xenon.