Methods such as GC, GC-MS, Py-GC and Rock-Eval were used for study on the typi cal fresh-water lacustrine oil shales from China, and it was suggested that warm and humid climate conditions are favourable to the growth and occurrence of fre shwater algae which are the major precursors of high potential source rock. In shallow lakelake basin bog transition facies or delta front facies there are i nputs of terrestrial plant materials which form organicrich oil shales contani ng ⅡⅢ transition type kerogen, and these shales are of mediumlow oil poten tial