Abstract: Initial alignment is one of the key SINS technologies, and alignment precision affects the navigation precision of navigation system directly, while Kalman filter parameters and initial conditions affect the convergent time and accuracy in SINS ground alignment. The effect is greater and usually leads to non-convergence and subsequently, low-accuracy SINS. The analytic alignment method is recommended based on a systematic study of this approach. In this study, the analytic expressions of javascript:void(0); nertial instrument errors were derived. The relationship between alignment time and instrument error were analyzed. Test results show that alignment accuracy can be close to the limitation using the analytic method. Meanwhile, up accelerometer bias can be correctly estimated, but the influence by random walk on the estimation results of gyro drifts cannot be ignored.