The invention discloses a method for synthesizing chiral five-member carbocyclic purine nucleoside by asymmetric transfer hydrogenation, and belongs to the field of asymmetric synthesis in organic chemistry. By taking racemic alpha-purine substituted cyclopentanone 1 as a raw material, formic acid and triethylamine in appropriate amounts are added in a dioxane solvent under the existence of a chiral ruthenium catalyst, and five-member carbocyclic purine nucleoside 2 with two chiral centers is obtained through dynamic kinetic resolution. A chiral five-member carbocyclic purine nucleoside compound obtained through the method is good in reaction diastereoselectivity and enantioselectivity, only a cis-form product can be obtained, the highest enantioselectivity can be up to 99 percent, and a trans-triazole purine nucleoside derivative can be obtained through further deriving of the product.