Temperature stress testing (TST) methods can simulate temperature and stress changes under real construction conditions, which can assess more accuracy performance of concrete compared with traditional methods. Considering the special early-stage properties of low-heat Portland cement concrete, its thermal and mechanical properties of are investigated using conventional testing methods and TST in this study. The results show that the compressive and axial tensile strengths of low-heat cement concrete measured by conventional tests are lower than those of medium-heat cement concrete before 28 days, but higher at the 90-day and 180-day ages. The elastic modulus and ultimate tensile values of both low-heat and medium-heat cement concrete are similar across all ages. The TST method indicates that the coefficient of linear expansion of low-heat cement concrete decreases sharply between 1 and 3 days, stabilizing at approximately 5.1 × 10–6/℃ after 3 days. The elastic modulus and tensile strength of low-heat cement concrete measured by the TST method are 47.2% to 68.2% higher than those obtained by the conventional test method. The differences in elastic modulus and tensile strength between the two test methods decrease with age.