Abstract: The degrading process of concrete performance usually accompanies with the development of pores, microcracks and cracks in it, and acoustic emission (AE) generating behavior is closely associated with the presence of non-uniform deformation or microcracks. The equation relating the damage evolution to AE characteristic parameters in concrete under uniaxial compression is derived, combining the AE rate process theory with damage mechanics, consequently, the damage of concrete can be quantitatively defined by using AE parameters. The procedure is applied to concrete-core samples taken from an existing bridge and the stress history of concrete is assessed by analyzing Kaiser- and Felicity-effects in the AE test. The experimental results verify the effectiveness and accuracy of AE technique in the quantitative damage estimation of concrete.