Bovine Serum Albumin (BSA), a model protein, was used to study the relationship between the free radical production and oxidative properties in the microwave field. Electron paramagnetic resonance (EPR) trapping with 5,5-dimethyl-l-pyrrolin N-oxide (DMPO) was used for the detection of free radical produced by BSA under different microwave treatment conditions. The signal intensity of free radicals arose from BSA solution via the increasing of power, temperature, and time after microwave irradiation. By measuring the carbonyl, thiol and surface hydrophobic oxidative properties of BSA under different microwave temperatures. It was showed that the carbonyl content increased, the thiol content decreased, and the surface hydrophobic content increased first and then decreased slowly with the increase of microwave temperature. Combining the results of free radical formation and oxidative characteristics during microwave irradiation, it was suggested that the microwave treatment of BSA should be carried out under the conditions of 400 W, 60 ℃, and longer time, this condition reduces the effect of BSA oxidation characteristics.