A method for synthesizing an antitussone medicine intermediate benzyl acetone includes the following steps that 320 ml of cyclohexane is added into a reaction container provided with a stirrer, a reflux condenser, a dropping funnel and a thermometer, 1.3 mol of stannous chloride is added in batches, 2.3 mol of ethyl acetoacetate is added, the stirring speed is controlled to be 130-160 rpm, reaction is conducted for 60-90 min, the temperature of the solution is raised to 65-70 DEG C, reflux is conducted for 3-5 h, 2.6-2.8 mol of benzyl amine (3) is dropwise added, dropping time is controlled to be 3-4 h, and a reflux reaction is conducted for 3-4 h to produce an intermediate product; the temperature of the solution is reduced to 10-15 DEG C, 330 mol of potassium bisulfite is added, and reflux continues for 4-5 h to generate an oily product; oxalic acid is added to adjust the pH of the solution at 4-5, reflux continues for 4-6 h, reduced pressure distillation is carried out, fractions at 95-105 DEG C are collected, washed with a saline solution and acetonitrile and re-crystallized in nitromethane, and crystal benzyl acetone is obtained.