Abstract: Preparation method for a compound as shown in formula (I) and levo-praziquantel. A racemate of ester of the compound of formula (I) is used as a substrate, and reaction is performed under the catalysis of immobilized lipase to produce the compound of formula (I); a circulating fluidized bed reactor is used, the circulating fluidized bed reactor includes an external circulation system and a reaction column, the immobilized lipase is arranged in the reaction column, the substrate solution is circulated many times between the external circulation system and the reaction column, the reaction is performed in the reaction column. The preparation of levo-praziquantel includes the described preparation steps of the formula (I). The preparation method of formula (I) can significantly improve the utilization rate of enzyme and reduce the use ratio of enzyme/substrate, and has mild reaction conditions, strong stereoselectivity, high reaction efficiency.