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The generalized phonon density of states for the high-T c superconductor YBa 2 Cu 3 O 7.1 with high Meissner effect (50%) and for its retreated sample with low Meissner effect (15%) at T=300 K and T=86 K respectively was measured by using inelastic neutron scattering method. The density of states of the superconductor YBa 2 Cu 3 O 7.1 at temperatures of both 300 K and 86 K shows a similar energy spectrum below 95 meV. However, above this energy there are evident softening of modes at 86 K. In addition, a large decrease of 92 meV peak in the density of states for a sample with lower Meissner effect was observed, this effect is supposed to be a result of an increase of vacancies on O 4 site.