The invention provides a stockyard dust emission inhibitor as well as a preparation method and an application thereof. The stockyard dust emission inhibitor is prepared from components forming the formula in parts by weight as follows: 5-20 parts of oxidized starch, 0.8-2.0 parts of modified cellulose, 2-10 parts of EVA emulsion, 0.6-0.8 parts of polyvinyl alcohol, 0.1-1 part of an emulsifier, 0.2-2 parts of a penetrant, 0.05-0.2 parts of a coalescing agent and the balance of water. The preparation method of the stockyard dust emission inhibitor comprises steps of preparing the oxidized starch, pretreating the raw materials, premixing the raw materials and mixing and stirring the raw materials. The dilution ratio and the spray times are determined according to the actual dust capacity, the dust emission inhibitor is diluted with water in a ratio of the dust emission inhibitor to water being 1:(10-20), then the solution is injected into high-pressure spray equipment and uniformly sprayed to the surfaces of stock piles in the dosage of 1.5 L / m<2> or higher, after the solution is dried, a polymer solidified layer with certain strength is formed on the stock surface, and stockyard dust emission inhibition is completed. The stockyard dust emission inhibitor is stable in quality, good in film-forming performance, high in solidified layer strength and wide in suitable material range, improves the environment after spray, can resist heavy weather and is long in spray cycle.