Abstract: Ni40.5Co32.5Al27 alloy ribbons were heat treated by 3 different methods.The microstructure was observed by OM.Martensitic transformation temperatures and damping capacities were investigated by differential scanning calorimetry (DSC) and dynamic mechanical spectroscopy (DMS).A bamboo-liked big size recrystallized grains was formed after water quenched from 1 623 K×5 h.Uniform fine γ phase deposited out by fast cooling (10 K/min) to 1 273 K and big size γ phase deposited out by slow cooling (0.5 K/min) .A damping peak appeared in the martensitic transformation temperature range of 371-415 K in cooling process.The damping peak value increased with the decreasing of oscillation frequency.After complete martensitic transformation,the damping capacity still increased with the decreasing of temperature.The damping capacities of Ni40.5Co32.5Al27 alloy ribbons increasd with the increasing of grain size and were higher than 0.04 at ambient temperatures.It is indicated that Ni-Co-Al alloy is a promising new damping material.