Trajectory planning with collision avoidance plays an important role for the safe application of multi-UAV systems in low altitude airspace. Although the synchronous DMPC algorithm had been widely applied in multi-agent systems due to its lower communication and computing cost, it generally suffers from the strict requirements. For example, the additional terminal conditions significantly reduce the maneuverability of the UAV in the fleet, whereas which ensure the stability of the algorithm and the feasibility of recursion. To remedy the raised issues, in this paper, a novel set of terminal conditions is proposed, which effectively reduces the conservativeness of the collision-free trajectories and satisfies the requirements of collision avoidance algorithms simultaneously. In this research, we also leverage the theoretical qualitative analysis, and thus providing initial guesses and related parameter settings for the algorithm. Finally, sufficient numerical simulations are proposed to verify the effectiveness and superiority of the proposed algorithm.