Abstract: Abstract: Electron spin resonance (ESR) spectroscopy was used to study the change of free radicals generated by the Maillard reaction of glucose and β-Lactoglobulin in the food-heating process, especially the change of free radicals caused by the changes of the temperature and pH. The relationship between Maillard reaction and the radicals in Maillard reaction can be determined by analyzing the change of the radicals in order to establish a simple and accurate method to evaluate Maillard reaction. Under the conditions of four different temperatures, three pH levels and with or without oxygen, the radical change trend of Maillard reaction was investigated that the radicals increased from 1.7×104 to 2.4×104 and the max reaction speed appeared from 90 min to 5min with temperature rise from 50-80℃. The radicals increased from 5×103 to 2.4×104 and the reaction sped up with pH rise from 5.0 to 8.0. The radical's amount raised and the radical signal intensity were higher under anaerobic conditions with pH increasing. When radicals were accumulated to a certain concentration, the signal strength dropped and finally disappeared due to its own collision or polymerization. Compared with the radicals of two types of substrates, the radicals of products of the Maillard reaction in type, quantity and rate of formation. It is proved that the stable signal of radicals obtained by the spin trapping can effectively present the reaction trend of radicals in the early and middle stages in the Maillard reaction of food heating, and it is easy to reflect the change of Maillard reaction. Compared with the traditional detection methods of the Maillard reaction, ESR spectroscopy is a simple and sensitive method of radical detection, and can be used as an important research method of Maillard reaction for food heating.