To address the problem that research on temperature control and crack prevention of mass concrete dams is divorced from actual construction information, this study takes the flood discharge and sediment flushing bottom outlet dam section of a medium-sized concrete gravity dam as the research object. A three-dimensional thermo-mechanical coupling finite element model is established, incorporating four types of construction information (corridor plugging, overwintering insulation, surface insulation, and water pipe cooling) to accurately simulate the entire pouring process. By analyzing the influence of construction information on the temperature and stress fields of the dam, high crack risk areas are identified, and a quantitative reinforcement scheme is proposed based on the tensile stress balance method. The results show that the synergistic effect of the “internal cooling + external insulation” temperature control measures can reduce the average maximum temperature of the dam by 16.1 ℃ and the average maximum tensile stress by 33.6%. High crack risk areas are concentrated in the keyway, near the corridor, and the internal area of the dam without water pipe cooling; the stress concentration factor near the corridor reaches 1.5, and the tensile stress exceeds 3.5 MPa under natural conditions.