Abstract: A method based on piezoceramic transducers and a wave analysis method was developed for monitoring crack damage of concrete structures. The monitoring mechanism how crack influences the stress wave propagating in concrete was analyzed. A discriminate method for damage degree was proposed and a damage approximate locating method based on a transducer array was employed according to the characters of civil engineering structures. At last, a validation test was conducted for different reinforced concrete members with the proposed method. Piezoelectric sensors were buried into concrete in form of smart aggregates in pairs. One sensor was used to transmit signals and the other to receive the signals. The damages were monitored and identified by the proposed method. The test results were agreed with the situation of crack damages. It indicates that the proposed method could reflect the developing tendency of damage well and it is suitable to be used for service state mornitoring of concrete structures.