The ruthenium-Cp* picolyl-NHC complexes catalyzed transfer hydrogenation reaction has been investigated with the aid of density functional theory calculations at the B3LYP level of theory. Two kinds of "hydridic route" (inner sphere mechanism) and one "direct hydrogen transfer route" (Meerwein-Ponndorf-Verley mechanism) have been examined. From the results we conclude that the stepwise inner sphere mechanism would be favored from the energetic point of view. The hemilability of the picolyl group plays an important role in determining which mechanism the transfer hydrogenation reaction should be followed. And the effect of agostic interaction has also been discussed. The ruthenium-Cp* picolyl-NHC complexes catalyzed transfer hydrogenation reaction has been investigated with the aid of density functional theory calculations at the B3LYP level of theory. Two kinds of "hydridic route" (inner sphere mechanism) and one "direct hydrogen transfer route" (Meerwein-Ponndorf-Verley mechanism) have been examined. From the results we conclude that the stepwise inner sphere mechanism would be favored from the energetic point of view. The hemilability of the picolyl group plays an important role in determining which mechanism the transfer hydrogenation reaction should be followed. And the effect of agostic interaction has also been discussed. [GRAPHICS] .