The garnet-muscovite geothermometer was refined through empirical calibration by using natural rocks metamorphosed under the physical conditions of 238-1306 MPa and 490-700℃. Input temperatures and pressures were determined through simultaneously applying the garnet-biotite geothermometer and the garnet-biotite-plagioclase-quartz barometer, assuming that all FeO in muscovite and garnet be ferrous. Garnet was treated s,s the asymmetric quaternary solid solution, and muscovite as the symmetric binary solid solution. Input muscovite compositions include Fe atoms between 0.03-0.19 and Mg atoms between 0.04-0.16 on the basis of 11 oxygen atoms, and input garnet compositions include spessartine fractions between 0.01-0.289, grossular fractions between 0.028-0.273, and the Fe/Mg ratio between 3.387-18.986. The resulting garnet-muscovite geothermometer reproduces temperatures within ±50℃ compared with the garnet-biotite thermometer. Total random error of ±37℃ of the new thermometer may stem from the pressur The garnet-muscovite geothermometer was refined through empirical calibration by using natural rocks metamorphosed under the physical conditions of 238-1306 MPa and 490-700 ° C. Input temperatures andpartments are determined by applying the garnet-biotite geothermometer and the garnet-biotite- Plagioclase-quartz barometer, which says that all FeO in muscovite and garnet be ferrous. Garnet was treated s, s the asymmetric quaternary solid solution, and muscovite as the symmetric binary solid solution. Input muscovite compositions include Fe atoms between 0.03-0.19 and Mg atoms between 0.04-0.16 on the basis of 11 oxygen atoms, and input garnet compositions include spessartine fractions between 0.01-0.289, gross fraction fractions 0.028-0.273, and the Fe / Mg ratio between 3.387-18.986. The resulting garnet-muscovite geothermometer reproduces temperatures within ± 50 ° C compared with the garnet-biotite thermometer. Total random error of ± 37 ° C of the new thermometer may stem from the pressur