In view of the limitations of the use of existing inertial frame alignment algorithms without latitude , there is an error accumulation phenomenon caused by the latitude estimation error. An optimized initial alignment method based on damped Gauss-Newton iteration without latitude is proposed in this paper. First of all, a new inertial frame alignment model is constructed, during the constructing process of latitude-related gravity vector, separating the latitude information-related items, to reduce the effect of the latitude estimation error on the accuracy of the model. And then the gravity visual motion principle is adopted to estimate latitude, and the damped Gauss-Newton iteration is adopted to solve non-linear least square question, which can solve constant attitude quaternion. Finally, for the error source in the gravity vector under the inertial solidification coordinate frame, real-time wavelet noise reduction and adaptive Kalman filter（RWD-AKF）algorithm are designed to optimize and reconstruct it, to further improve the latitude estimation accuracy and alignment accuracy. Sway simulation trial proves: compared with existing latitude-free alignment method（TVA）, the proposed alignment method without latitude results in a heading alignment accuracy improvement of more than 30%, close to the conventional OBA alignment accuracy. The proposed alignment method can effectively realize the alignment of the SINS without latitude, to improve the flexibility and universality of SINS.