In order to reduce dust pollution on the road of open-pit coal mine transportation, RL-SPI foam dust suppressant was prepared by using natural biodegradable soybean protein isolate (SPI) and biotype surfactant rhamnose lipids (RL) as the main reagents, supplemented by sodium alginate（SA） and sodium chloride（NaCl） as additives. The experimental characterization results showed that the viscosity of the dust suppressant solution at a concentration of 0.5 % was 25.5 mPa·s. The compressive strength of the hardened layer formed on the surface of coal dust after spraying is 0.52 MPa. Under the condition of level 9 wind speed in the laboratory simulated roadway, the dust suppression efficiency was maintained at 94.23 %. In addition, Fourier transform infrared spectroscopy and scanning electron microscopy were used to analyze the mechanism of action of dust suppressants. Fourier infrared spectroscopy analysis showed that there was a chemical bonding between the dust suppressant and coal dust, and compared with water, the dust suppressant had a stronger hydrogen bonding effect with coal dust, which increased the hydrophilicity of coal dust and made it more wettable. Scanning electron microscopy further showed that there was a significant cementation effect between the treated coal dust particles. Therefore, the RL-SPI foam dust suppressant prepared in this study can effectively inhibit the diffusion of dust in coal mines and significantly reduce environmental pollution.