Abstract: The initial alignment of INS is a very important procedure. It is very valuable to the INS used in various weapon system and civil system that the best alignment accuracy is obtained in the shortest time. Because of the poor observability of INS on stationary base,the estimation of the azimuth error will converge very slowly in initial alignment by means of Kalman filter. A fast estimation method of the azimuth error is creatively proposed for the initial alignment of INS on stationary base. On the basis of the fast convergence of the leveling error,the azimuth error can be directly calculated.By means of this fast initial alignment method, the time of initial alignment is reduced greatly. The computer simulation results illustrate the efficiency of this method.