Abstract: Acoustic emission (AE) phenomenon occurs with damage process of loaded concrete structures, and the accumulation of damage affects the energy attenuation effect of AE signal. To furtherly explore the correlation mode between material damage and AE signal energy attenuation, and then use the energy attenuation law to quantitatively characterize the degree of concrete damage, AE monitoring was carried out for the entire failure process of reinforced concrete beams under three-point bending loads, and the energy attenuation coefficient was calculated in real time with the help of the damage location results. The development of concrete damage can be divided into three stages according to the time-history change of the attenuation coefficient and a method based on AE energy attenuation coefficient was proposed to assess concrete damage. The test result showed that the method can quantitatively evaluate the damage of the concrete specimens in real time, and give an early warning to the transition of the bearing mode after the macroscopic cracking of the specimen occurs.