The isotopic exchange between NaH¹⁴CO3 and HCOONa has been found to occur both heterogeneously and homogeneously.The heterogeneous exchange takes plane on glass surface at lower temperature range (30-180℃),while homogeneous exchange occurs mainly above 200℃ and only the latter exchange was shown to be a process via an oxalate intermediate.The exchange kinetic equation~derived.The activation energy of the heterogeneous exchange is 1.4 keal/mol,while that of the homogeneous one is 6.4 keal/mol.The rate constant of the heterogeneous exchange is found to be 6.8 x 10^-2 mol/L·hr.