Quartz as a pressure gauge and its accuracy were studied by Raman spectroscopy at 25 ℃ and ambient pressure. The result shows that even at same temperature and pressure, the Si—O vibrational mode［1, 2］ for different grains of quartz varies between 463.59 and 464.65 cm-1, with (±0.1-±0.3)cm-1 error. The maximum difference of various grains of quartz is up to 1.06 cm-1, much higher than the measurement error. The authors believe that the variety is resulted from the stress in the internal grains of quartz, which formed during crushing quartz into small grain. Therefore, Raman spectrum for quartz has to be firstly measured as a reference of zero pressure at ambient pressure and temperature in the experimental study by using diamond anvil cell. In addition, wavenumber drift of the spectrometer and the unstable temperature will also cause remarkable error for measuring pressure.