A great petroleum exploration potential exists in Shuangcheng-Taipingchuan area in Songliao Basin. Analyzed crude oils from Fuyu-Yangdachengzi oil layers have similar geochemical characteristics. The distribution of n-alkane plots is complete and show single peaks with the main peak carbon of C23, unconspicuous odd-even predominance in which parts of crude oils are light carbon predominance. The characteristics of biomarkers are: (1) relative high contents of tricyclic terpane, (2) relative high contents of gammacerane, pregnane and homopregnane, (3) V-shaped distribution of regular sterane. The carbon isotope value is generally small. It is demonstrated that the biological sources of crude oil would mainly be composed of low-grade aquatic organism and thallophyta as well as higher planet, and the source rocks would had been deposited in brackish water reducing-fresh water oxidated environment. These crude oils have similar characteristics in generally and have similar biological sources and organic facies but some differences exist in thermal maturity of these crude oils. According to biomarker parameters, the crude oils are divided into three families: low thermal maturity oil, low-middle thermal maturity oil and middle thermal maturity oil, among which low-middle thermal maturity oils are common. It is suggested that an attention should be paid to the area of low thermal maturity oil favorable for exploration.