The external boundary of a dam guide wall is very sensitive to temperature change. Cold waves will cause sudden temperature drops that lead to large temperature gaps between the surface and the internal of the concrete guide wall, resulting in excessive temperature stress and temperature cracks. Taking the right guide wall of Xunyang Hydropower Station as an example, the three-dimensional finite element method was used to simulate the construction process of this dam section. The temperature field and stress field were simulated under three scenarios, namely, no insulation and no cold wave, no insulation with cold wave and insulation with cold wave. The results show that the cold wave has a great influence on the surface temperature of the wall, and produces a large tensile stress on the surface; however, it has little effect on the internal temperature and stress of the dam section. When the cold wave hits, the thermal insulation of Polyfoam sheet with a thickness of 5 cm can increase the surface temperature of the wall by about 8.0 ℃, and the maximum stress on the surface is less than the acceptable tensile stress for abrasion-resistant concrete on the overflow surface. So this measure can effectively avoid the occurrence of temperature cracks caused by cold waves. The research results can provide some reference for similar engineering projects.