The combined die with uniform changeable interference under the preload condition was designed by the finite element software. This combined die could effectively reduce tangential compressive stress of gear root in the getter zone to avoid the die damage with wire cutting. But the tangential compressive stress of gear root in forming zone of die core reduced accordingly, which could not fully offset the tensile stress during extrusion forming, and the die life was affected. In order to solve this problem, the design method of local changeable interference on combination die was put forward, namely, uniform interference was applied on the upper part of die core, while changeable interference was used on the lower part of die core. Therefore, the tangential compressive stress of gear root in forming zone of die core under the preload condition was not reduced, and the tangential compressive stress of gear root in the getter zone was only decreased to improve the die life. Furthermore, for the gear with modulus of 4, the cone angle γ″=1°  and  γ′″=1.2° as well as the height 21 mm of uniform interference zone were determined respectively by numerical analysis, and the actual production was carried out. Thus, for the combined die with uniform changeable interference,the die life was prolonged by obout 35%.