Abstract: The steady-state and dynamic process simulation of the cryogenic rectification process of isotope C-13 was researched. The commercial process simulation software Aspen Plus was used to establish the steady-state model of the cryogenic rectification process. The reliability of the model was validated by the comparison of the simulation result and the experimental data. It showed that the technological process design of high quality C-13 can be conducted with software Aspen Plus. The dynamic process model was built with software Aspen Dynamics. The simulation results with the models were well supported by experimental ones. It showed that the dynamic characters of the separation process can be investigated with Aspen Dynamics. Then, the dynamic start-up time, control scheme analysis, operability analysis, and safety analysis etc. can be implemented with dynamic simulation.