When cracks occur in concrete, released fracture energy will be proportionally transformed into the energy contained in acoustic emission (AE). According to this physical phenomenon, AE technology provides an effective monitoring method for fracture process of concrete through acquiring generated AE. However, such monitoring is limited in qualitative evaluation of fracture process under most occasions. Quantitative interpretation of fracture process is difficult to accomplish by simply acquiring the amount of AE generated or conducting parameter-based AE analysis. This paper investigates the feasibility of reflecting the fracture energy released during fracture by means of evaluating the energy index of detected AE signals. An effective fracture model based on fracture behavior of concrete cylinder under uniaxial compression is introduced here to provide a mathematical relationship between acquired AE energy index and crack formation energy of concrete. Apart from reasonably estimating the energy consumed for crack formation, cement-based piezoelectric sensors are embedded inside the concrete to carry the task of detecting AE and transforming its energy into the electrical energy of AE signals. On the basis of experimental study, the energy of detected AE signal is satisfactorily correlated to the corresponding fracture energy and quantitatively represents the fracture energy releasing process of concrete during the period of stable cracks development. © 2012 American Society of Civil Engineers.