Blunt aortic injury in vehicle crash accident may occur at any moment of the cardiac cycle. However, there is currently a lack of in-depth understanding within the industry regarding the effects of hemodynamic characteristics at different physiological stages on the mechanical response of the aorta under seatbelt restraint loading. Based on a heart-aorta finite element system, this study developed a physiologically characteristics fluid-structure interaction (FSI) model and validated its hemodynamic simulation reliability. On this basis, a stepwise modeling strategy was employed to establish a thorax-enclosed visceral organs FSI model under seatbelt restraint loading. Numerical simulation analyses of different physiological stages of the heart during systole (early, mid, and late) were conducted by varying the boundary conditions of left ventricular motion displacement and aortic outlet pressure. The results indicate that, during the rapid ejection phase (mid-systole), there is a higher risk of aortic injury under seatbelt restraint loading. During the rapid ejection phase, the aortic arch region exhibits a peak strain of 0.148 at 0.12 s, representing 9.4% and 6.1% increases compared to early-systole and late-systole phases, respectively. The peak blood pressure at the outlet of the descending aorta reaches 18.31 kPa at 0.08 s, which is 14.7% and 9.6% higher than that in the early and late systole, respectively. The established thorax-viscera integrated FSI model under seatbelt restraint loading demonstrates the capability to simulate hemodynamic responses of the aorta under complex loading conditions, providing a technical reference for analyzing physiological state-dependent aortic injury mechanisms.