Aiming at the requirement of land weapons for high accuracy north seeking,taking high accuracy FOG north-seeker as the research object,based on error model of FOG north-seeker and error characteristics of FOG,the error of FOG North-seeker is analyzed in theory,and error sources of north-seeker are introduced,which mainly include system error and device error. The north seeking errors caused by different error sources are deduced,the results show that north seeking precision of FOG north-seeker mainly depends on gyro drift,installation error and angle measurement accuracy. The simulation experiment on north seeking error caused by various error sources of FOG north-seeker was carried out. The experimental results prove the validity of the theoretical analysis.