Abstract: The examination of the marine kerogen samples from the Xuefengshan area, Hunan was carried out by a laser Raman microspectrometer. There are two distinct vibration peaks G and D in the wave number range of 1000-2000cm^-1. The distances between the peaks G and D display regular changes, as a function of vitrinite reflectances (Ro). Within the vitrinite reflectances Ro<2.4%, the distance between the peaks G and D rapidly increases in response to the increase of vitrinite reflectances. In this instance, the correlation coefficient is 0.82. No marked relationship was observed when the vitrinite reflectances range between 2.4% and 2.9%. The distance between the peaks G and D gradually decreases as the vitrinite reflectances Ro>2.9%. In this instance, the correlation coefficient is 0.88. It follows that the vitrinite reflectances may be an important index of organic maturity and thermal evolution. The relationship between the Raman spectra and vitrinite reflectances indicates that the laser Raman microspectrometry may be employed as a new technique suitable for the examination of organic maturity and thermal evolution of sedimentary organic matter.