The invention provides a method for synthesizing substituted alpha-hydroxyphenyl acetonitrile, wherein in the presence of an alkali serving as a catalyst, aromatic aldehyde reacts with hydrocyanic acid to form the substituted alpha-hydroxyphenyl acetonitrile; the alkali serving as the catalyst is an organic polymer catalyst, and the organic polymer catalyst is a nonvolatile polymeric amines compound. The method provided by the invention has the beneficial effects that since a heterogeneous catalyst is adopted, after the reaction, the catalyst can be recycled by simple filtration and activation, which not only solves the problem that the catalyst cannot be separated from the reaction system after the catalytic reaction to result in product pollution, but also greatly saves the catalyst cost and is green and environmentally friendly; stable storage and long-term transportation of the substituted alpha-hydroxyphenyl acetonitrile are very important for subsequent production, and the production cost and the application safety of the substituted alpha-hydroxyphenyl acetonitrile can be reduced.