The invention relates to a chili seed coating agent and a preparation method thereof. The chili seed coating agent comprises, by weight, 3-5 parts of gibberellin, 1-3 parts of auxin, 2-4 parts of indoleacetic acid, 5-7 parts of modified starch, 0.5-1 part of bone glue, 0.5-1 part of potassium sulfate, 0.1-0.3 parts of zinc sulfate, 0.5-1 part of curcumin, 2-3 parts of agarose, 1-2 parts of tolclofos-methyl 20% missible oil, 0.3-0.5 parts of carbendazim, and the balance of water. The preparation method comprises the following steps: placing the agarose, modified starch and bone glue in 100 parts of pure water, heating the agarose, modified starch, bone glue and water until boiling in order to dissolve the agarose, modified starch and bone glue in the water, cooling the obtained solution, keeping the temperature of the cooled solution at 60-65 DEG C, adding remaining substances in the above formula to the solution, uniformly mixing the remaining substances and the solution, and cooling the obtained solution to 40-50 DEG C in order to obtain the seed coating agent. The seed coating agent has the advantages of enhancement of the disease resistance of seeds, reduction of the mildew rate, shortening of the germination time, promotion of growth of seedlings, increase of the output of the crops, and improvement of the quality of products.