Abstract: Moving long baseline(MLBL) algorithm based on extended Kalman filter(EKF) for cooperative navigation and localization of multiple AUVs(autonomous underwater vehicles) is proposed.In MLBL-based multi-AUV cooperative navigation structure,the master AUV is equipped with high precision navigation system,and the slave AUV is equipped with low precision navigation system.They both are equipped with acoustic devices to measure relative location.The moving long baseline algorithm combines proprioceptive and exteroceptive information,and gets the real time position of slave AUV.The math model of cooperative navigation system is developed,and a cooperative navigation algorithm based on extended Kalman filter is designed.The analytical results derived in this paper are validated with simulation in different test cases,and navigation performances of EKF algorithm and geometric equation algorithm are compared.The research results prove that the navigation accuracy of AUV group is improved effectively by using EKF algorithm in the condition that master AUV is used as moving long baseline node.