The invention relates to the technical field of organic synthesis and discloses a preparation method of O-alkylphenylthiophosphate. The preparation method comprises adding sulfonyl chloride and alkyl phenylphosphonite into an organic solvent, adding a copper salt catalyst and L-proline ligand or bipyridyl ligand into the solution, carrying out a reaction process at 50 to 100 DEG C for 2 to 10h, after the reaction, concentrating the reaction solution, and carrying out separation and purification to obtain O-alkylphenylthiophosphate. The cheap and easily available sulfonyl chloride and alkyl phenylphosphonite are used as raw materials, an alkaline environment is avoided, and the product is obtained under the conditions of a catalytic amount of a copper salt and ligands. The preparation method has the advantages of wide application range of a substrate, simple processes, operation convenience, wide substrate range, good yield, and promotion and application feasibility. The product can be used in fields of medicines and pesticides.