Abstract: It is pointed out that the vehicle acceleration in the navigation frame affects the accuracy of SINS(strapdown inertial navigation system) directly after analyzing the effect of damp network on the system.Then,the premise and fault of a series of fuzzy damp algorithms in some interrelated documents is discussed and an improved algorithm is proposed.In this algorithm,the three accelerometer outputs are transformed and compensated by the attitude and velocity outputs of the SINS,and are denoised with a fixed point smooth filter.Finally the processed data is input to the fuzzy arbiter to distinguish whether the damp network can be used in the SINS.The simulation and actual test on sea proved that this algorithm can identify the vehicle motion and change the damp state of SINS more suitably.The 46-hour navigation data on sea shows that the system vehicle error decreased to 1 m/s from 2 m/s because the SINS choice it’s damp state properly by means of this algorithm.