In order to meet the requirements of launch vehicle, the SINS has gradually replaced the complex optical aiming system with self-alignment technology. Aiming at the problem that the Kalman filter converges slowly in the initial alignment, a rapid self-alignment method for launch vehicle based on low-pass filter is proposed. Based on the self-aligning algorithm of the solidification inertial frames, the self-alignment real-time solution is realized by using the two-vector construction scheme of the moving window. A low-pass filter is introduced at the rear end of attitude transfer matrix between solidified inertial frames to reduce the harmful acceleration caused by the lever arm effect and ensure the self-alignment accuracy. The method does not need to carry on complex Kalman filter operation and converges quickly. It is also simple to realize engineering. Digital simulation and experiment data show that the self-alignment method of the solidification inertial frames based on low-pass filter can achieve the same accuracy of Kalman filter and shorten the alignment time within 5min. Finally, these results show the validity of the method.