Abstract: The influence of microwave irradiation on the stability constant of Cr (III) complexes and their coordination process, reacted by Carboxylate complex (formate ion and oxalate ion) and chromic nitrate, were studied with Equimolar concentration and UV-vis spectrophotometry. The results indicate that the stability and rate of complexing reaction of of Cr(III) complexes formed were both accelerated by microwave irradiation compared with water bath heating, because of the violet shift of maximum absorption wavelength, increased complex ratio and stability constant.