An integrated orbital design method with relaxation of temporal constraints is presented, focusing on improving the efficiency of complex-flight-mission planning for manned lunar exploration. Crewed lunar exploration programs are characterized by a variety of spacecraft and multiple trajectory stages. The aim of integrated design is to realize automatic splicing of such multistage trajectories under coupled temporal and spatial constraints. Currently, integrated mission–orbital design is mainly achieved through decoupling and iterative methods, and the matching of boundary constraints usually requires human-in-the-loop intervention. In this paper, a novel integrated orbital splicing process is proposed from the viewpoint of the temporal dimension, considering the temporal relationships between orbital stages and the scheduling flow of the underlying dynamical models. Relaxation factors are introduced for weak temporal constraints to improve the overall convergence of orbital splicing calculations across different stages. A comprehensive temporal constraint model and subsequently an integrated orbital design model are constructed. The proposed method is validated by simulation of flight missions targeting the high-latitude regions of the moon.