Concrete samples were tested by multi-function triaxial instrument under cycle load condition with different strain rates. The relationship between acoustic emission signals and stress level was analyzed, and the damage evolution regularity was researched from the aspect of acoustic emission hit number. Furthermore, a single-parameter model that only contains cycle number was established to estimate damage value. The results show that 1) under different strain rates, the paths of damage evolution are not identical. Damage accumulation degree at earlier stage is bigger than that at later stage when the strain is small, and damage curve is flat at later stage; 2) the damage evolution path moves forward with the increase of strain rate, and the value of damage development along with the increase of strain rate presents a regularity that first increases then decreases with the increase of cumulative residual strain. When cumulative residual strain is certain, the damage development degree at two adjacent strain rates weakens with the increase of strain rate; 3) the regularity of concrete damage evolution under cyclic loading and unloading is featured with three phases, which can be reflected by statistical density function.