[Purposes] This study aims to explore the influence of wax-based warm mix agents on the microscopic characteristics of asphalt and wax precipitation. [Methods] Two commonly used commercial wax-based warm mix agents, Sasobit and Asphaltan, were selected as research objects. The mixing mechanism of warm mix agents and asphalt was qualitatively analyzed by infrared spectroscopy test, and the changes in wax crystals during wax precipitation were quantitatively analyzed by variable temperature polarizing microscope test. The mechanism of action of warm mix agents in asphalt and its influence on the process of wax precipitation in asphalt were deeply discussed. [Findings] Compared with Sasobit，the Asphaltan warm mix agent also has carbon-oxygen double bonds. There is no complex chemical reaction between wax-based warm mix agents and asphalt, and only physical co-solubility is observed. The wax precipitation rate of asphalt decreases with the decrease in the temperature and finally tends to be stable. At the same time, the number, average size， and area fraction of wax crystals increase. The wax crystals are connected to form a network structure as they grow. Moreover，the wax precipitation process in warm mix asphalts is affected by temperature and cooling rate. A slower cooling rate helps to form more complete and orderly wax crystals. [Conclusions] Wax-based warm mix agents affect the precipitation process of wax crystals in asphalt mainly through the physical co-solubility effect. Optimizing the cooling rate can significantly improve the structure and properties of wax crystals, thereby improving the overall performance of warm mix asphalt.