Finite element simulation of the effects of mould angle and friction condition on the equal channel angular pressing (ECAP) for AZ80 magnesium alloy were investigated by using DEFORM-3D program. The results show that the curve of load-displacement was divided into several stages including rapid increasing stage, load fluctuation, rapid increasing stage, steady stage and rapid drop stage. Firstly, when the angle decreased from 150°to 90°, the maximum load increased, and the same as energy consuming. In addition, the average effective strain increased with the decreasing of mould angle after single extrusion, while the degree of effective strain uniformity of the sample decreased and keep greater strain grads between inner and surface part. Secondly, the work load ascended with the increasing of the friction coefficient from 0 to 0.3, and one part of load overcome the friction and the other part is used for deformation of the sample. With the increment of friction coefficient, the average effective strain keeps steady value, while the degree of effective strain uniformity of the sample decreased. As mentioned above, large angle mould and low coefficient of friction should be adopted during ECAP deformation for AZ80 magnesium alloy.