Abstract: A n umerical simulation analysis was conducted for the extrusion of large-diameter thick-walled HT700P Fe-Ni based superalloy seamless pipe, and trial production was carried out. The high-temperature rheological stress curve of HT700P Fe-Ni based superalloywas measured using Gleeble-3500 experimental machine, and the high-temperature rheological stress data of HT700P Fe-Ni based superalloy were integrated into the Deform software, a numerical simulation model of the extrusion process was established to analyze the extrusion loading force at different heating temperatures. The simulation results show that when the billet heating temperature is 1170 ℃, the extrusion load force is not more than 34500 tons.Combined with the numerical simulation results, the billet heating temperature of 1170 ℃ was selected, and a 36000 tons vertical extrusion machine was used to complete the extrusion trial production of a large thick wall HT700P Fe-Ni based superalloy seamless pipe with the size of φ559 mm×80 mm×L(L≥3000 mm). The one-time trial production was successful,and the maximum loading force in the actual extrusion process was 32500 tons. The inner and outer surfaces of pipe fittings are smooth and without visual defects, which provides basic technical support for subsequent batch manufacturing.