Abstract: The kinetics of precipitation of AlN in austenite of oriented silicon steel was calculated by the theory of second phase precipitation.The results show that the critical nucleation sizes of AlN in austenite under different nucleation mechanisms are identical and the critical nucleation size increases with the increase of temperature.The critical nucleation energy of AlN at grain boundary is the smallest,the relative nucleation rate is the largest and the precipitation time is the shortest.Although the critical nucleation energy of homogeneous nucleation and dislocation nucleation is equal,the relative nucleation rate of homogeneous nucleation of AlN is 2～3 orders larger than that of dislocation nucleation,and the initial precipitation time of homogeneous nucleation is also shorter than that of dislocation nucleation.The main nucleation mechanism of AlN in austenite is controlled by grain boundary nucleation.