The particle size and distribution of asphalt are affected by the preparation process and formulation of emulsified asphalt. The study found that the correlation ratio between the particle diameter of emulsified asphalt and the viscosity has put forward a mathematical model. When other influencing factors remain unchanged, the particle size distribution has a The influence trend of viscosity is that with the increase of the median particle size of the emulsified asphalt and the widening of the particle size distribution of the emulsified asphalt, the Engla viscosity of the emulsified asphalt gradually decreases. On the contrary, the particle diameter of emulsified asphalt is unimodal, and the viscosity of emulsified asphalt with smaller particle size is larger. The focus of the value is that the viscosity of the emulsified asphalt with a bimodal distribution of particle diameters is several times lower than that of the unimodal emulsified asphalt with the same solubility.