Due to the disturbance caused by wind and wave, the traditional alignment methods are no longer applicable to the strapdown inertial navigation system. The newlyderived attitude determination based alignment （ADBA）has been widely approved as a promise alternative scheme due to its advantages in terms of alignment speed and disturbance robustness. However, the ADBA is virtually a coarse alignment method, which can not compensate the sensor errors. This drawback make the roll angle estimate by ADBA possess divergent error, which can much degrade the alignment performance of ADBA. In order to overcome this drawback, this paper proposes to align the roll angle using only very short outputs of inertial sensors while align the pitch and yaw angles using more data. The simulation and experimental studies were carried out to validate the proposed method.