The tight oil refers to the oil that accumulates in oil shale or interbedded tight sandstone reservoirs adjacent to source rocks and with surface-air permeability less than 0.3mD. Generally,this accumulated oil has not yet experienced large-scale and long-distance migration,and tuus its accumulation mainly develops in a semi-deep to deep lake zone,typically in the oil shale and tight sandstone of Chang-7 internal. Tight oil in Ordos Basin is characterized by a wide distribution, superior conditions of source rocks,tight sandstone reservoirs,complex pore-throat structures,poor physical properties,high oil saturation,better oil properties and low pressure coefficient.The tight oil shows a density of0.84～0.86g /cm3 and a main peak at nC15 in the whole hydrocarbon chromatogram．The tight oil consists mainly of light hydrocarbons, low content of aromatic hydrocarbons, and has an equilibrial ratio of Pr / Ph, varing from 0.85 to 1.10, and －31.7‰ ofδ13CPDB for the whole crude． Its terpane distribution is characterized by relatively abundant rearranged hopanes, low content of gammacerane, and high ratios of Ts / Tm, The steranes in the crude mainly consist of rearranged steranes, while ααα-20R sterane isomers display an asymmetric“V”type distribution pattern, representing a typical lacustrine-derived oil．According to the characteristics of high C30-rearranged Hopane and extremely low C30 Hopane of the Chang71 tight oil,and the characteristics of low C30-rearranged Hopane and extremely high C30 Hopane of the Chang72 tight oil in combination with other geochemical parameters in oil-source correlation, Chang71、Chang72 reservoir tight oil has a close relationship with Chang7 black mud shale and oil shale source rock in the Maling region .