This paper introduces the theoretical model of mechanical alloying. In view of the varied angle in the actual impact process, the Gauss distribution of angle is drawn into the model based on the angle factor. The distribution of temperature rise is obtained and fitted. It accords well with the Gauss distribution in some extent. The results show the thermal effect of powder depends on milling technology, the impact angle and others. Compared with the previous models, the presented model is well in consistent with the fact.