Abstract: The microstructure, martensitic transformation, pseudoelasticity and damping properties of the Co39Ni34Al27 alloy quenched at different temperatures from 1 200 to 1 350 ℃ were investigated by optical microscopey, differential scanning calorimetry, cyclic tensile test and damping test. The results show that with the increase of quenching temperature, the grain size of the alloy increased, the γ phase content decreased and the β phase was gradually transformed into martensite phase. The martensite transformation temperatures were almost linearly proportional to the quenching temperatures. The alloy quenched at 1 250 ℃ showed a significant pseudoelasticity performance. The damping capacity of the alloy after quenching at 1 250 ℃ and 1 320 ℃ reached the peak values during the martensitic transformation, which were 0.042 and 0.035 respectively. The damping capacity of the alloy quenched at 1 320 ℃ was larger than that at 1 250 ℃.