For tracking the ground target with unknown maneuvering under gust disturbance,a global stable control policy is proposed for quad-rotor UAV.The control system is divided into position and attitude subsystems.In position subsystem,to the problem of no relative velocity measurement between the target and UAV,a bounded-output sliding mode position controller with observer is designed,which command outputs are in the specified range.The corresponding quaternion attitude controller is designed by using nonlinear switch term to achieve fast convergence.Therefore,the global stability property of the whole position-attitude system is achieved.Finally,the gust is modeled and the simulations of maneuvering target tracking missions show satisfactory tracking performance even in the wind field.