The high pressure and high-temperature behavior of MnCO3 was investigated up to 55GPa at ambient temperature and up to 573K at ambient pressure by Raman spectroscopy, respectively. Some new modes were detected at approximate to 16 and approximate to 32GPa, which were assigned to MnCO3-I below 16GPa and to MnCO3-II above 32GPa, and to a coexisting phase of them in between. The high pressure vibration properties of all Raman modes, especially high frequency modes, were systematically reported. The coexisting phase of MnCO3-I and MnCO3-II had much easier compressibility than the MnCO3-II phase. The thermal stability of MnCO3 was at least to 573K and its thermal expansion along the c axis was easier than a and b axes.