The authors studied the fluorescence change of immobilized lipase from Rhizomucor miehei in the microwave assisted enzymatic esterification of caprylic acid and butanol in organic medium by investigating the fluorescence spectra in solvent or aqueous buffer after incubating the lipase with the solvent,caprylic acid and butanol under microwave irradiation,respectively.A comparison was made with the conventional heated enzymatic esterification in the solvents.Both of the heating modes,the microwave irradiation and conventional heating,can enhance the fluorescence intensity without shifting the emission wavelength of the lipase.In the circumstance that the irradiation can accelerate the esterification,the irradiation can enhance the exposure of the lipase protein molecules in the aqueous environment after incubating the lipase with solvents or the substrates.The effect of the reaction mixture on the fluorescence intensity was dominated by the solvents.The trend of the plot of log P versus the initial reaction rate was similar to that of log P versus fluorescence intensity of lipase in aqueous buffer after esterification;but was different from that of log P versus fluorescence intensity of lipase in organic medium.