The kinetics of oxidation of α-alanine by dihydroxydiperiodatonickelate (Ⅳ) ion was studied by spectrophotometry in aqueous alkaline medium. The reaction rate showed first order dependence in okidant, and positive fractional order dependence in α-alanine. It was found that the pseudo first-order ([Ala]_o>>[Ni(Ⅳ)]_o) rate constant, k_(obs), increases with the increase of [OH~-] and decreases with the increase of [IO~-_4], which implies that before the rate-determining step there is a preequulibrium in which one of the periodate ligands of the oxidant is deprotonated and the other is dissociated. Under the protection of nitrogen the reaction system does not induce polymerization of acrylamide indicating that an innersphere one-step two-electron tranfer is involved in the oxidation. Based on the experimental results a mechanism involving a preequilibrium of an adduct formation between Ni(IV) and α-alanine has been proposed. The rate equations derived from the mechanism explained all the experimental results satisfactorily and the preequilibrium constants, rate constant of the rate-determining step together with the activation parameters were evaluated.