The invention discloses an intermediate for synthesizing carbapenems penicillin etapenem having the formula of V, and a preparation method and application in the preparation of the carbapenems penicillin etapenem thereof. The preparation method comprises the following steps: allowing a compound having the formula of IV and methylsulfonyl chloride to react in a nonpolar solvent in the presence of organic alkali reagent as catalyst, wherein PMB is shown in figure in (1), PNZ is shown in figure (2), and Ms is methanesulfonyl. The intermediate can be used for preparing etapenem side chain, and further etapenem. The preparation method can be carried out at the room temperature, with the advantages of mild reaction condition, low cost, simple operation, simple experiment condition, no requirement for expensive reagent, high yield no requirement for refining, environmental friendliness, and easily realized industrial production.