The invention discloses a chemical synthesis method of oxcarbazepine, which comprises the steps as follows: adding 5-cyan-11-nitro-5H Dibenzoyl nitrogen heterocyclic shown in formula (III), Raney's nickel catalyst and organic solvent to a reactor, charging hydrogen till the pressure of the hydrogen reaches 2-20atm, performing the reduction reaction completely at 40-120 DEC C, filtering to obtain the filtrate, adding 20wt%-36.5wt% of hydrochloric acid for hydrolyzing completely, concentrating the reactant, and cooling for crystallization to obtain oxcarbazepine shown in formula (I). The reaction equation is described as follows. The synthetic route has the advantages of advanced technological line, simple and safe operation, higher product yield and purity and wide industrialized prospect.