Abstract: With the continuous increase in large-scale engineering projects, large-volume structures are encountering quality control issues during the concrete pouring process. To ensure the quality of construction, higher requirements are often placed on the design strength, setting time, and other related properties of concrete. In addition, concrete integration and one-time pouring are required. The coupled effects of cement material hydration heat, boundary constrained stress, and environmental humidity are often encountered during the pouring process of large-volume concrete. This is because cement-based cementitious materials release significant hydration heat in the early stages of pouring, while the concrete has poor heat transfer performance. This results in thermal expansion and contraction owing to internal and external temperature differences, storing large stresses and easily causing cracks in concrete structures, thereby affecting their durability and integrity. This study focuses on large-volume poured-concrete structures, utilizing finite element analysis software to establish a three-dimensional numerical model of thermal mechanical coupling. It simulates the temperature field distribution characteristics and evolution law of structural cracks of poured-concrete structures at specific construction times under four different concrete-pouring temperatures. The results show that there is a positive correlation between the molding temperature and the temperature rise of the structure. Lowering the molding temperature of concrete can reduce the peak structural temperature and narrow the temperature difference, which is beneficial for controlling the generation and evolution of concrete cracks. As the molding temperature decreases, the temperature transition zone between the concrete boundary and the interior becomes less pronounced. This is because when the temperature decreases, the heat transfer from the deep structure to the surface layer decreases. Accordingly, the heat exchange efficiency between the surface boundary and air decreases. When the molding temperature is high, the deep structure transfers more heat to the surface layer, causing a significant increase in surface temperature. However, the surface boundary has a relatively high heat exchange efficiency owing to boundary effects and temperature differences, resulting in a rapid decrease in temperature. The heat exchange efficiency is affected by the temperature difference between the surface temperature and external air medium. When the mold temperature decreases, the heat transfer from the deep structure to the surface decreases, and the heat exchange efficiency between the surface boundary and the air decreases accordingly. However, its heat exchange efficiency is still higher than that of the non-boundary part of the surface, reflecting an unclear temperature transition zone. The concrete at the central depth exhibits the highest structural temperature, which facilitates the accumulation of tensile stress in the concrete structure. At different molding temperatures, the peak structural temperature and maximum hydration temperature rise curves are approximately linear. The peak crack length reflects a positive correlation with three parameters: molding temperature, peak structural temperature, and maximum hydration temperature rise. However, note that when the molding temperature increases from 10 ℃ to 15 ℃, the peak crack length significantly increases. As the temperature of concrete entering the mold decreases, the number of large cracks on the surface continue to decrease and gradually shift from a distribution pattern of intersecting large cracks to that of uniformly dispersed small cracks in space.