Supercritical CO₂ Brayton cycle has become one of the most promising technologies for solar thermal utilization, a clear understanding of system’s dynamic performance is necessary to the efficiency and smooth operation of the unit, while the property changes of CO₂ near the critical point put forward higher requirements. In this article, a dynamic system model is proposed to analyze the responses of the system under different input perturbations, which emphasizes the effect of drastic changes in the properties of supercritical CO₂ on system’s dynamic performance. The results show that an increase in heat source input and a decrease in cooling water mass flow rate will increase the overall system operating temperature, but the parameters in lower pressure side are less sensitive to the perturbations, which is conducive to the unit stability; Conversely, the overall system temperature drop, resulting in the compressor inlet fluid being in the two-phase region and thus affecting system performance. Meanwhile, the impact of turbine rotational speed on system performance is negligible compared to the impact of main compressor rotational speed. The analysis of the dynamic response developed in this paper lay the foundation for the control strategies.