Provided are R-praziquantel preparation methods, which utilize the characteristics of biological enzyme of strong stereoselectivity, site-selectivity, and regioselectivity, of high resolution efficiency, of mild reaction conditions, and of simple operations to catalyze the hydrolysis of a certain enantiomer in a chemically synthesized racemate or a derivative, thus acquiring a mixture of reacted and unreacted optical isomers. R-praziquantel prepared by the method can have a purity of 98% or more.