Abstract: With the Gleeble 1500 hot-deformation simulation testing machine,the relationship between the temperature, the strain rate and the deformation resistance are investigated. And the computation formula for the extrusion pressure for the Incoloy 825 alloy is set up,and the pressure value is worked out. The changing status of the extrusion pressure during the whole extrusion process is studied by means of simulating the stress and strain rate as present at all points in the said process via the FE software Deform. As a result it is identified that comparing relevant data resulting from the software-made simulation,the theoretical calculation and the actual operation, it is found that all the max.extrusion pressures occur at the breakthrough stages,and that the theoretical extrusion pressure is slightly different from the one as used for actual operation.