Abstract: To investigate the distribution of thermal stress during the continuous casting of monolithic elements for inland immersed tunnels, a typical immersed tunnel was selected as the engineering background. A numerical method validated against reduced-scale model tests was employed to examine the mechanism of early-age temperature-induced cracking in the tunnel element. Particular attention was paid to the thermal stress distribution in the newly and previously cast concrete of adjacent casting sections, with the aim of identifying the critical locations for crack control and determining the ranges over which a newly cast section affects the temperature and stress fields of the previously cast section. The results show that the heat released by cement hydration in the newly cast concrete alters the original thermal boundary conditions near the interface, resulting in a secondary temperature rise in the interface region of the previously cast section. Under the combined effects of temperature variation and restraint imposed by the newly cast concrete, a band-shaped tensile stress concentration develops near the interface of the previously cast section. Comparison between single-section casting and multi-section continuous casting indicates that the significant influence of a newly cast section on the longitudinal temperature field of the previously cast section is mainly confined to the vicinity of the interface. Under the conditions considered in this study, the affected range is approximately 1.7 times the thickness of the main slab. By contrast, the stress-affected range depends on the structural location and restraint conditions and should therefore be evaluated separately for different regions.