Abstract: Taking the petroleum geolgy of the southern Songliao Basin as background,based on the geological and geochemical condition of the generation of natural gas,this paper studies the analytical data of 320 gas samples and finds out that the natural gases of the southern Songliao Basin could be divided laterally into districts and vertically into zones.According to the organic geochemistry characteristics,four genetic types of gases are recognized.Furthermore,the favourable areas and the guideline for natural gas exploration in southern Songliao Basin are pointed out.