By internal friction technique，the behaviors of quenched-in vacancies and their influence on the reverse martensitic phase transformation (MT) temperature of the Cu-11.9Al-2.5Mn (wt%) shape memory alloy have been studied. Investigations on the specimens subjected to various cooling regimes indicate that rapid cooling rate leads to relatively high reverse MT temperature. For the water-quenched specimens，the reverse MT temperature bears a non-monotonic relationship to quenching temperature. This phenomenon may be related to the different formation energies of vacancies in ordered and disordered phases.