Raman spectra of aragonite and calcite were studied in the temperature range of 18～388 ℃ and pressure range of 79～2 014 MPa, and 19～351 ℃ and 96～1 823 MPa, respectively in the diamond anvil cell. The relationships among the Raman shifts of aragonite and calcite, the system pressure and temperature were obtained. The Raman shifts of aragonite and calcite become higher with the pressure increasing, and become lower with the temperature increasing except the Raman shift of 704 cm-1 of aragonite. The absolute values of νi/T of aragonite and calcite for the lattice modes are greater than those for the internal modes of the CO3 groups, and the values of νi/T and νi/P of aragonite and calcite are various. The Raman shifts of the internal CO3 modes are related to the C—O bond length and the C—O bond is more compressible and less expansible in calcite than in aragonite, besides, they may be also related to the dynamical effects of the CO3 groups accompanying the aragonite-calcite transition.