Abstract: Based on attitude error equations of typical dual-axis-index Inertial Navigation System(INS),influence of angular motion of vehicle is theoretically analyzed.The angular motion,coupled with scale factor and installation error,can deteriorate precision of INS,and produce a new type of error.Scale factor error leads to DC component,which is equivalent to un-compensable constant drift of gyroscope,and has great effect on INS.Installation error leads to AC component,which is equivalent to periodic oscillating drift of gyroscope,and has limited influence on INS.Results of experiment verifies the mentioned conclusions.