The invention provides an asphalt separant and a preparation method thereof. The asphalt separant is uniform light yellow emulsion and comprises, by weight, 4-10 parts of dimethyl silicone, 1-2 parts of surface active agents, 4-10 parts of glycerol, 40-80 parts of plant oil, 20-60 parts of water, 0.5-0.8 part of preservative and 0.2-0.3 part of aromatic. The preparation method includes the following steps that all the components are pre-heated to 60-80 DEG C, the dimethyl silicone oil, the glycerol and the plant oil are sequentially added into a reaction kettle with the constant temperature of 60-80 DEG C, the surface active agents and the water are added after stirring is carried out for 10-20 min, then stirring is carried out for 10-20 min, high-speed shearing emulsifying are carried out for three times through a colloid mill at the rotation speed of 1000-6000 r/min, and the preservative and the aromatic are added in the emulsifying process, and the asphalt separant is prepared. The asphalt separant has the advantages of being environmentally friendly and free of pollution, and is soluble to water, good in chemical stability, excellent in high temperature and low temperature resistance, little in use amount and excellent isolation efficiency. Influences to performance of asphalt mixed materials are small, and the asphalt separant can be used for adhesion resistance of various mechanical devices in asphalt mixed material conveying and construction, and is wide in application range.