The invention discloses a coal dust inhibitor and a preparation method thereof. The coal dust inhibitor comprises an organic binding agent, a penetrating agent, a humectant, a de-foaming agent and water, wherein the organic binding agent comprises polyacrylamide and polyvinyl alcohol; the humectant comprises hydroxypropyl methyl cellulose, sodium carboxymethylcellulose and glycerol. The preparation method of the coal dust inhibitor comprises the following steps: mixing components in following (1) or (2) and uniformly mixing: (1) the organic binding agent, the penetrating agent, the humectant, the de-foaming agent and water; (2) the organic binding agent, the penetrating agent, the humectant, the de-foaming agent, an pH adjusting value, color modulation emulsion, an auxiliary agent and water. The coal dust inhibitor has a high speed of forming a cured protection layer and has proper mechanical strength and water resistance; the preparation method is simple and has the characteristic that needed production equipment is little. The coal dust inhibitor can be used for dust inhibition of coal transportation, storage, construction sites and the like.