Abstract: The characteristicts and distinctions between both the automatic and artificial determinations of vitrinite reflectance are compared and analyzed.The method and conditions of automatic determination,which are highly correlated with the results of artificial determination,are given.The determining results indicat that the result repeatabitity by automatic determination is better than that by artificial one,and the resolution capability is equal between them.After the results by automatic determinations transformed to those by artificial one,the deviations with the latter are less than the error ranges of the artificial determinations carried by different research units.