The tethered Unmanned Aerial Vehicle (UAV) is a new type of aircraft developed for long-duration aerial tasks, which combines a rotorcraft with a ground tethered unit.In actual operation, the launch and recovery of a tethered cable will lead to changes of dynamic performance of the tethered UAV, which will affect its trajectory tracking control, and so does the lumped disturbances which contains unmodeled dynamics and gust disturbances.To solve the above problems, a robust adaptive Sliding Mode Controller (SMC) based on the disturbance observer is proposed.Firstly, the catenary theory is introduced to describe the tension of the tethered cable.The dynamic model of the whole system is established by using Newton-Euler equation.Secondly, under the framework of Lyapunov theory, the disturbance observer is used to estimate and compensate for lumped disturbances and an adaptive SMC is designed to ensure the convergence of trajectory tracking errors.Finally, the effectiveness of the proposed controller is verified through the analysis of simulation cases and experiment.The results show that the proposed controller has a higher trajectory tracking precision compared with the terminal SMC and it can help the tethered UAV to track complex trajectories.