The present invention relates to a synthesis method of hydroxybenzylamine, belonging to the technical field of organic synthesis. The principle of the method is a demethylation reaction of methoxybenzylamine in the presence of hydrobromic acid. The present invention has the characteristics that methoxybenzylamine and hydrobromic acid are distilled at reflux to remove redundant water to improve a reaction temperature and increase the concentration of hydrobromic acid in a reaction mixture, thereby enhancing the demethylation of hydrobromic acid on methoxybenzylamine and then shortening a reaction time and increasing a conversion rate; when generation of a methyl bromide gas is not observed, distillation is continued, excess hydrobromic acid is recycled to further improve the reaction temperature and increase the conversion rate and meanwhile reduce the consumption of raw material hydrobromic acid and decrease the processing capacity of the subsequent steps and the consumption of raw material sodium hydroxide.