Abstract: The oil sands resources are interpreted as the significant unconventional oil and gas resources in China. The emphasis of the present paper is placed on the chromatographic analysis and mass spectrographic analysis of eight pieces of oil sands samples from the Upper Ganchaigou Formation (N₁) in the Youshashan area in order to examine ancient sedimentary environments, maturity and origin of parent matter types. The results in this study show that the saturated hydrocarbons range between 0.53 and 0.81, indicating higher oil contents. The m (Pr)/m (Ph) ratios vary from 0.43 to 0.26, with an average of 0.32 (8), indicating a relatively deep-water and highly reducing environment of the source rocks. The parameters for oil sands evolution mC₃₁αβ22S/22 (S + R) and mC₃₂αβ22S/22 (S + R) are more than 0.5 or 0.6, indicating that all the eight oil sands samples are maturated oil sands samples and subjected to biodegradation. The triangular diagram of the parameters of steranes C₂₇, C₂₈ and C₂₉ indicate that the parent matter types of the oil sands belong to the lower aquatic organisms mixed with higher plants. The oil sands in the study area have higher contents of saturated hydrocarbons, wider outcropped area and greater thickness, and thus may be considered highly prospective for the unconventional oil and gas resources.