This article deals with the novel of the kinetics of oxidation of Vitamin-D3 by N-sodio-N-chlorobenzene sulfonamide or Chloramine-B (CAB) in pH-5.0 buffer has been investigated flurometrically at 303K. Studying effects of various parameters on oxidation of vitamins help us in understanding the metabolic functions. Since vitamins are important part of our body and diet as well. Results obtained indicate second order with respect to [H+] show that protonation of oxidizing species RNHCl- to give RNH2Cl. Further it is observed that the fractional order on [Vitamin-D] and first order dependence on [CAB]. Addition of reaction products benzenesulfonamide or bromide ions and variation of ionic strength of the medium have no influence on the reaction rate. The reaction has been studied at different temperature and activation parameters have been calculated. A general mechanism constituent with the preceding kinetic data has been proposed and the rate law derived.