Indirect ELISA of deer's brucellosis belongs to the veterinary field and is used for diagnosing deer's brucellosis to improve the diagnosis level of the prior art. Biomaterials used in the assay of the invention comprise pig brucella vaccine 2 (S2) as an antigen, an enzyme labeled antibody rabbit anti-deer IgG-HRP, a standard positive serum, a standard negative serum and a serum to be assayed; and the assay comprises the following steps: coating the antigen, washing, adding the serum, adding the rabbit anti-deer IgG-HRP, adding a substrate liquid, terminating a reaction, testing by an enzyme-linked detector, adjusting to zero at 490nm, testing the OD value of each hole, and determining the result is positive when the OD value is equal to or greater than 0.32. According to the invention, the S2 is used as the antigen, the rabbit anti-deer IgG-HRP is used as the enzyme labeled antibody, and the indirect ELISA is used to diagnose the deer's brucellosis, so compared with previous diagnosis methods, the indirect ELISA of the invention has the advantages of good specificity, sensitivity and repeatability, and accurate diagnosis.