The extrusion forces of the spray-formed Al-25wt%Si alloy at various strain rates and temperatures were calculated with the flow stresses obtained from high temperature compressive tests. The compressive stress-strain curves of the spray-formed Al-25wt%Si at various temperatures and strain rates were determined and discussed. The constitutive equation of strain rate as a function of stress and temperature described by, n Q RT A e ' / sinh( ) − ε& = ασ for the spray-formed Al-25wt%Si alloy, was established. The activation energy and constants in the constitutive equation were discussed and compared to other Al alloys. A direct extrusion experiment was employed to evaluate the extrusion loads vs. ram displacement at various temperatures and strain rates. By applying the constitutive equation, the extrusion loads were calculated and compared to the experimental ones for various temperatures and strain rates. The accuracy of the calculated results compared to the experimental results was discussed.