Abstract: For formation tracking control of multiple fixed-wing UAVs (unmanned aerial vehicles), there are significant challenges in systematically tackling input saturation constraints, external input disturbances, and safety constraints of collision avoidance among UAVs. To solve this problem, a distributed and robust control law for obstacle avoidance and cooperative formation is proposed based on higher-order control barrier functions. Firstly, a nominal robust formation tracking control law for multiple fixed-wing UAVs is designed without initially considering obstacle avoidance constraints, which satisfies input and velocity constraints. The proposed nominal control law is based on sliding mode control methods, and can implement precise formation tracking control in the presence of bounded input disturbances. Secondly, some improved high-order control barrier functions are designed with the input constraints taken into consideration, for the obstacle avoidance among the UAVs, and between the UAV and the obstacle, respectively. The obstacle avoidance constraints for linear control inputs are derived in the presence of external input disturbances, based on the invariant set theory. Finally, a local quadratic programming problem is formulated for each fixed-wing UAV, based on the nominal formation tracking control law and the robust control input constraints for obstacle avoidance, and the final robust tracking control law for obstacle avoidance and safe formation can be obtained by solving this problem. Simulation examples demonstrate that the proposed control law can effectively handle the disturbances compared to the control laws without considering external input disturbances, and can reduce system oscillations and better handle UAV speed constraints compared to the control laws based on potential function methods. Additionally, it achieves significant improvements in computation time compared to the control laws based on distributed MPC (model predictive control) methods. The above results validate the innovation and effectiveness of the designed control law.