Abstract: This paper deals with the study on kerogen using Py-GC method. Samples were heated to 500℃ rapidly and stayed for 10 minutes. All the thermo-degradational products were collected and analysed on a Varian-3700 Gas Chromatograph. The components determined were classified into normal alkane, normal alkene, isoprenoid alkane, isoprenoid al-kene and alkyl benzenes (naphthalene) and so on. After analyzing and comparing components of thermo-degradational products of two low rank coal kerogens and two oil shales, reliable informations on the composition of precursors, organic type, maturity and sedimentary environment of organic matter in source rocks study are acquired.