Preparation method of salicylonitrile

The invention discloses a method for synthesizing salicylonitrile by using ortho-hydroxybenzamide as a raw material, dioxane or tetrahydropyrane and tetrahydrofuran as catalysts, and dimethylbenzene or benzene, methylbenzene and chlorobenzene as solvents through introducing phosgene at a refluxing temperature. The reaction formula is described in the specification. The invention relates to a method for preparing the salicylonitrile without generating waste water and waste slag. Compared with the prior art, the method has the advantages of less reaction byproducts, high quality, high yield, simplicity and safety in operation, low price and easily available raw material, the content of the salicylonitrile is not less than 98 percent (liquid chromatogram, external standard method), and the yield of the salicylonitrile is not less than 95 percent (in the terms of o-hydroxybenzamide).