The extrusion process for large-scale thick-walled INCONEL625 pipe was investigated by DEFORM-2D simulations. The influent significances of the process parameters including initial temperature of billet (P), initial temperature of dies (M), extrusion speed (V), friction factor (F) as well as extrusion ratio (λ) and die structure geometrical parameters angle of bottom die (β), profile radius of bottom die (R1, R2) as well as bear length (L) to the extrusion load peak (ELP) and temperature peak (TP) at the die exit of the pipe were obtained through orthogonal regression analysis. The results show that the parameters of P, F, V, β and λ have more significant influences than other parameters. The regression models of ELP and TP related to the parameters of P, F, V, β and λ are created through stepwise regression, and using the developed regression models the reasonable span of these parameters are obtained as following: F=0.01~0.02, V=100~200 mm/s, P=1000~1250 oC, β=35°~50° and λ=4.5~7. Based on the above results, the extrusion limit map has been established for the extrusion process of large-scale thick-walled INCONEL625 pipe, which can be used to fast design the feasible extrusion parameters