This paper proposes a new flight tube planning method aimed at debris avoidance for launch vehicles. Due to frequent space activities, the number of space debris is rapidly increasing. Existing methods for handling debris constraints mainly focus on refining guidance laws or optimizing trajectories around a given reference trajectory. The fuel consumption of the launch vehicle depends on the selection of this reference trajectory, which lacks global planning capabilities in dense space environments. This paper addresses the problem by introducing a global topology graph to represent available flight tubes for debris avoidance. As the corner of the stone, the spatio-temporal flight windows are established using the Voronoi graph, which takes debris at various typical orbit altitude levels as generators. These windows are then interconnected across different orbit altitude levels to create the flight tube graph model. Based on the model, the flight tube planning approach constrained by trajectory planning constraints is proposed. This approach involves interactive execution where graph search is conducted to find a flight tube, while trajectory planning within the flight tube is performed using iterative second-order cone programming. Simulation results show the global advantages in fuel optimal value for debris avoidance.