The microstructural evolution of the supersaturated ZA27 alloy and its damping capacities were investigated during the natural aging. The investigation showed that the microstructure of the alloy transformed from single beta phase into a fine mixture of equiaxed alpha, eta and epsilon grains during the process. The maximum of the interface area in the alloy existed during the aging. Microstructure changes were accompanied with the variance of damping capacity. It was found that the damping capacities increased quickly and greatly at the beginning of aging and then it decreased gradually and finally reached a constant during the following aging. It is believed that two mechanisms are responsible for the occurrence of the damping behavior in supersaturated ZA27 alloy, i.e., interface damping and dislocation damping.