Abstract: Double-stage cascade simulation model for stable isotope ¹³C separation by cryogenic distillation was established, and the physical parameters of isotopes were embedded. The reliability of the model was verified by the experimental data which we had got. The errors of simulation results and experimental results were less than 10%.The effects of feed rate, out stream, inter-stage transmission and operating pressure on the abundance of product were analyzed, which would lay the foundation of subsequent optimization design work.