Abstract: A dynamic model of the carbon monoxide cryogenic distillation system was set up to deeply study the dynamic characteristics of the system in which the isotope ¹³C was enriched. The processes of total reflux, startup and fluctuation of material of the system were studied by dynamic simulation software, Aspen Dynamics. The effects of boiling power and bottom holdup in total reflux were studied, the balance time of total reflux was about one week, and the mole fraction of ¹³C¹⁶O at the bottom of the column was about 3.9%. The startup program that first enriching then product outputting can reduce the startup time of the setup, and the balance time with the mole fraction of ¹³C¹⁶O reached to 14.5% was 38.6 d; however, the balance time with feeding and outputting at the same time was 127.7 d. The development of lower holdup packing will shorten the startup time, and then reduce the cost of products. The fluctuation calculation showed that the setup can preferably handle material fluctuation. When in a feeding and outputting fluctuation amplitude up to 50%, and the time lasting 4 hours, the changes of product quality can be neglected.