Physical hardening is one of the fundamental causes that affect the low temperature performance of asphalt. However, the mechanism of the effect of physical hardening on asphalt low temperature performance is not clear. Additionally, the low temperature performance evaluation system has not considered the effect of physical hardening. Therefore, these issues may lead to the failure of the low temperature performance evaluation. Aiming at solving these problems mentioned above, the study will start with analyzing the evolvement rule of asphalt microscopic characteristics undergoing physical hardening, and then analyzing the variation of asphalt molecular relaxation mode, molecular conformation and microscopic volume characteristics after the physical hardening. Based on the theory of fracture mechanics and rheological mechanics, the macroscopic mechanical behavior of asphalt under the physical hardening effect will be investigated. By combining the macroscopic and microscopic experimental results, the internal relations between microstructure change and macroscopic mechanical behavior will be interpreted, and the temperature stress constitutive model of asphalt materials under the physical hardening effect will be derived. Based on the results above, a sensitive and effective asphalt low temperature performance evaluation index, considering the effect of physical hardening, will be proposed..The project will reveal the mechanism of the effect of physical hardening on low temperature performance of asphalt, providing a theoretical basis for an accurate assessment of asphalt low temperature performance. It will also have certain reference for the development of low temperature anti-cracking material for pavement and facilitate the development of pavement computational mechanics and material science.