The dielectric properties of 0.75Pb（Mg1/3Nb2/3）O3-0.25PbTiO3 （PMN-25PT） ceramic under hydrostatic pressure and pressure-induced phase transition were investigated. PMN-25PT ceramic is pure perovskite with weak relaxation at 1 bar. With increasing hydrostatic pressure，the temperature，Tm，of top dielectric constant decreases，/+dTm/-dP≈-4℃/kbar，frequency dispersion and phase transition diffuse increases，remnant polarization decreased continuously. The hydrostatic pressure dependence of dielectric constant （ε） is similar to the temperature dependence of dielectric constant. The relax ferroelectric-paraelectric （RFE-PE） phase transition was induced by hydrostatic pressure and the transition was gradual change process with stronger relaxor behavior than by temperature-induced.