Abstract: In order to provide an effective method for non-destructive assessment of alkali aggregate reaction, an ultrasonic tomography algorithm using straight-line ray-trace method was used in this study to reconstruct wave velocity images of lab-prepared concrete specimen blocks, which visualized the internal status of the structure. On this basis, a wave velocity-based damage indicator is proposed to quantitatively evaluate the degree of alkali aggregate reaction through the relationship between wave velocity and concrete quality. The results show that the tomography method can effectively differentiate between reactive and non-reactive concrete specimens. In addition, the experimental results of the proposed method were compared with those of the electrical impedance spectroscopy method, which showed a strong correlation, further validating the reliability of the proposed method.