Circumlunar return and reentry spacecraft accurately landed within the predetermined area in SiZiWangQi, Inner Mongolia on Nov. 1, 2014, which marks the successful completion of the reentry test in the third phase of ChangE lunar exploring project, and indicates that the key technology of deep space reentry return, as the speed of the spacecraft is close to the second cosmic velocity, is fully mastered by China. It ensures the smooth implementation of ChangE-5 program and lays a solid foundation of the lunar exploring project. During the flight control of circumlunar return and reentry spacecraft, the integrated digital flight control support system (IDFCS) is played a key role in ether flight control strategy development, simulation & validation and design optimization. In this paper, the principle and architecture design of the IDFCS for Spacecraft is proposed, and the key points of the system, such as acceleration of processor simulation, virtual chip modeling, automatic test script, general user interface, data dynamic interpretation, are analyzed. Finally, the practical effect of the IDFCS for circumlunar return and reentry spacecraft is present. The actual in-orbit validation shows that some of the satellite flight control problems, such as the complexity of constraints, the difficulty of strategy determination, are solved by the present system, and rich experience in both theory and engineering is accumulated for the subsequent development of the satellite flight control system.