Abstract: A paths planning algorithm was proposed to solve the problem of dual-aircraft cooperative tracking and locating a maneuvering target with bearings-only measurements (BOMs) in 3-dimension situation. Its purpose was to improve the passive target tracking and localization performances. After the passive tracking extended Kalman filter(EKF) was set up, the mutual information metric function and the covariance control metric function were given. The target position geometrical dilution of precision (GDOP) was deduced by introducing the vector theory. Details of the paths' planning algorithm were put forward. Computer simulation studies indicate that the EKF-based method has a worse performance when the target has maneuvers. The GDOP-based method has a good adaptation to the maneuvering target.