Kinetic study of the polyurethane prepolymer formation between isophorone diisocyanate(IPDI), poly(oxytetramethylene)glycol(PTMG), and dimethylol alkanoic acid(DMPA, DMBA) were studied in the batch system by using quantitative in-situ IR spectroscopy. The reaction rate was obtained from monitoring the change of NCO (2265 cm^-1) and C=O (1725 cm^-1) stretching band in series IR spectra. The reaction is in accord with the first-order for the concentration of hydroxyl groups and isocyanate group respectively which conform to the second-order law entirely. The activation parameters obtained from the evaluation of kinetic data are ΔH^#=58.18 kJ/mol, ΔS^#=-95.98 J/mol·K and E_a=61.07 kJ/mol in bulk polymerization between PTMG and IPDI. also, The activation parameters inspected reaction of Dimethylol alkanoic free acid and IPDI of [NCO]/[OH] ratio of 1.0 at various temperature.