Method for preparing phosphine-containing alpha-keto ester through witting reaction

The invention provides a method for preparing phosphine-containing alpha-keto ester through a witting reaction. The method comprises the following steps: adding a halogenated pyruvate compound shown by a formula II as shown in the specification and triphenylphosphine into a first solvent, stirring, cooling, and filtering to obtain filter cakes; washing the filter cakes, and drying to obtain a precursor quaternary phosphonium salt of phosphine ylide shown by a formula III as shown in the specification; putting the precursor quaternary phosphonium salt of phosphine ylide shown by the formula IIIinto a second solvent, dropwise adding the second solvent in which an alkali is dissolved, further adding a solution of a compound shown by a formula IV as shown in the specification, evaporating offthe second solvent, further adding a third solvent, stirring, standing still, filtering to obtain first filtrate, concentrating, cooling, stirring, filtering to obtain second filtrate, and carrying out evaporation drying to o