The invention belongs to the technical field of dust pollution control, and discloses an environment-friendly biomass dust suppressant and a preparation method thereof. The dust suppressant is composed of carboxymethyl starch, carboxymethyl cellulose, sodium alginate, anhydrous Calcium chloride, rhamnolipids, sophorolipids and water. The dust suppressant of the present invention is low in cost, environmentally friendly, non-toxic and harmless, easy to biodegrade, has good biocompatibility with plants in the spraying area and the soil environment, and can be used in dust control work together with green plants to realize chemical dust suppression Comprehensive application with plant dust retention. When the dust suppressant solution is sprayed on the dust surface, it can form a continuous and certain-strength consolidation layer on the surface, which has good wind erosion and rain resistance performance, can withstand extreme temperature environment for a long time, and has certain moisture retention , which has a better effect of dust suppression and damage prevention.