In aqueous alkaline medium, the kinetics of oxidation of pectate biopolymer (Pec) by hexacyanoferrate(III) (HCF) has been studied spectrophotometrically under the conditions, [Pec] >> [HCF], at a constant ionic strength of 1.0 mol dm-3 and at 25 oC. The reaction showed first order dependence on [HCF], whereas the reaction orders with respect to both [Pec] and [OH- ] are less than unity. The oxidation rate was found to increase with the increase on the ionic strength and dielectric constant of the reaction medium. Initial addition of reaction product, hexacyanoferrate(II), did not has any significant effect the oxidation rate. Based on the kinetic results, a plausible mechanistic has been proposed which involves the formation of a 1:1 intermediate complex between HCF and the deprotonated pectate species in a pre-equilibrium step. The rate law associated with the oxidation mechanism is derived and the reaction constants involved in the different steps of the mechanism are calculated. The activation parameters with respect to the slow step of the mechanism along with the thermodynamic quantities of the equilibrium constants are also calculated and discussed.