The invention discloses a 5-bromo-6-chloro-3-indolyl caprylate synthesis method, which is characterized in that 4-chloro-2-aminobenzoic acid and N-bromosuccinimide are subjected to a bromination reaction to obtain 5-bromo-4-chloro-2-aminobenzoic acid, 5-bromo-4-chloro-2-aminobenzoic acid and sodium chloroacetate are subjected to a nucleophilic substitution reaction to obtain N-(4-bromo-5-chloro-2-carboxy)phenylglycine, N-(4-bromo-5-chloro-2-carboxy)phenylglycine is subjected to a cyclization decarboxylation reaction to obtain 1-acetyl-5-bromo-6-chloro-3-indole ethyl ester, and 1-acetyl-5-bromo-6-chloro-3-indole ethyl ester and octanoyl chloride are subjected to a selective esterification reaction to obtain 5-bromo-6-chloro-3-indolyl caprylate. According to the present invention, the 5-bromo-6-chloro-3-indolyl caprylate synthesis method has advantages of high efficiency, safety, environmental protection and relatively high total reaction yield, and can be used for the large-scale synthesis of 5-bromo-6-chloro-3-indolyl caprylate.