Abstract: Addressing the iron-nickel-based alloy UNS N08810 seamless tube, different expansion die shapes and four different cold-expanding deformation processes are designed.The FEA method is used to analyze the expanding deformation behaviors of the large-sized iron-nickel-based alloy UNS N08810 seamless tube under the conditions of different expansion die shapes, different expansion amounts, and different wall thickness parameters so as to get the expansion load curve and the change regularity of the OD and WT of the tube as expanded as well as the characteristics of the metal flow.Based on the simulation experiment result, the cold-expanding process experiment for the said seamless tube is also conducted so as to verify the reliability of the simulation experiment result.