The invention provides a synthesis method of an o-iodo-alpha-acyloxycarbonyl compound. The o-iodo-alpha-acyloxycarbonyl compound is synthesized under the catalysis of N-heterocyclic carbene precursor salt with an EBX reagent as a raw material and a mixed solution of an organic solvent and water as a solvent. Compared with existing methods, the method has a wide applicable substrate range, adopts mild reaction conditions and is simple and convenient to operate and high in reaction efficiency.