Abstract: The FGC (flying gage change) process on an actual 5-stand tandem cold mill by simulation was researched. First, its FGC simulation system was given and its technology to realize FGC was analyzed. Then a simulation was done on an actual 5-stand tandem cold mill. By detailed analyzing the results, It indicated the deficiency of current technology and advanced a measure to improve the mill's dynamic characteristics. Simulation results confirmed its effectiveness and feasibility.