Lightweight aggregate concrete (LWAC) is often used in building structures in these cold regions, which may also bear impact loads. To investigate the dynamic mechanical behavior of LWAC at low temperatures, this study conducted numerical simulations of the split Hopkinson pressure bar impact experiment on LWAC at room and low temperatures. The numerical simulation results showed good agreement with the experimental results, and on this basis, the dynamic failure process and characteristics of LWAC at different temperatures were analyzed. The numerical simulation results showed that both strain rates and temperatures have significant effects on the dynamic failure behavior of LWAC, and as the strain rate increases, more cracks are produced in LWAC during failure; as the temperature decreases, more cracks appear in the mortar matrix owing to the gradual decrease in the strength difference between the mortar matrix and the aggregate phase. In addition, both decreasing the temperature and increasing the strain rate enhance the strength of LWAC; a low temperature enhances the impact toughness of concrete at 60 s^-1 and 80 s^-1 but weakens it at 100 s^-1. This study can be used as a theoretical reference for the safety and protection design of LWAC in low-temperature environments.