Antiferroelectric-ferroelectric　(AFE-FE)　phase　transition　in　ceramic　Pb0.97La0.02(Zr0.75Sn0.136Ti0.114)O-3　(PLZST)　was　studied　by　dielectric　spectroscopy　as　functions　of　frequency　(10(2)-10(5)　Hz)　and　pressure　(0-500　MPa)　under　a　DC　electric　field.　The　hydrostatic　pressure-dependent　remnant　polarization　and　dielectric　constant　were　measured.　The　results　show　that　remnant　polarization　of　the　metastable　rhombohedral　ferroelectric　PLZST　poled　ceramic　decreases　sharply　and　depoles　completely　at　phase　transition　under　hydrostatic　pressure.　The　dielectric　constant　undergoes　an　abrupt　jump　twice　during　a　load　and　unload　cycle　under　an　electric　field.　The　two　abrupt　jumps　correspond　to　two　phase　transitions,　FE-AFE　and　AFE-FE.