The microstructural evolution of supersaturated ZAC27 alloy and its damping capacities were investigated systematically in the period of natural ageing. The investigation shows that the microstructure of ZAC27 alloy evolves as follows: after 1 day ageing, α phase, η phase andε phase appear in the alloy, moreover, the amount of α phase, η phase and ε phase increase with the increasing of ageing time; after 10 d ageing, the β phase decomposes and vanishes completely in the alloy; after 50 d ageing, phases gather and form the coarser equilibrium microstructure which consists of near equiaxed, shot club shaped α, η and ε phase. Microstructure changes accompany with the variance of damping capacity. It is found that the damping capacities varies quickly and obviously during natural ageing. The damping capacity reaches the highest value 7×10 -3 at the 10th day. Sequentially, the damping capacity decreases gradually, and reaches a constant value of 4×10 -3 after 50 d natural ageing. The damping behavior in supersaturated ZAC27 alloy comes from a superposition of two mechanisms: interface damping and dislocation damping. The reasons for the great change of damping capacity of supersaturated ZAC27 alloy are as follows: 1) the precipitation of η and ε phases from supersaturated β solid solution and 2) the interaction of dislocation with vacancies and solute atoms. The results also indicate that solid solution+water quenching+natural ageing is the best heat treatment technique to improve the damping capacity of the ZAC27 alloy substantially. <