Finite element simulation of the effects of mould angle on the equal channel angular pressing (ECAP) for Al-Zn-Mg-Cu aluminum alloy was investigated by using DEFORM-3D program. The results show that the work load ascended with the increasing of the mould angle and was divided into five stages including rapid increasing stage, steady stage, rapid increasing stage, steady stage and rapid drop stage. When the angle decreased from 150° to 90°, the maximum load increased by 2.87 times and the energy consuming increased by 2.36 times. In addition, with the decreasing of mould angle, the average effective strain increased after single extrusion, while the degree of effective strain uniformity of the sample decreased. There were greater strain grads between inner and surface part. As mentioned above, large angle mould should be adopted on ECAP for Al-Zn-Mg-Cu aluminum alloy in order to ensure extrusion smoothly and attain homogeneous fine grain.