Abstract: To solve the disputes about oil-source relationship in Yanchang formation of Daijiaping area, Ordos basin, the paper systematically analyzes the geochemical characteristics and accumulation periods of the oil in different horizons of Yanchang formation based on the analysis on the extract group components, saturated hydrocarbon gas chromatography-mass spectrometry and inclusion homogenization temperature test of the oil and source rock samples. The results show that the geochemical characteristics of the oil in different horizons are basically the same, indicating a fairly deep-deep lacustrine sediments formed in a fresh water-brackish water and weak reduction-reduction sedimentary environment. The kerogen is characterized by the mixtures of lower hydrobiont and terrestrial higher plant. The homogenization temperatures of the rock samples from different horizons of Yanchang formation in Daijiaping area show a feature of double-peak distribution, and the homogenization temperatures of the inclusions in the reservoirs of Chang 82 and Chang 9 are higher than those in reservoirs of Chang 6 and Chang 81. The analysis on the burial history shows that there were 2 oil charging periods, namely the end of Late Jurassic-the middle of Early Cretaceous. Using the parameters of biomarkers to do Q-type analysis, the oil of Yanchang formation can be divided into 2 types, TypeⅠincludes the oil from Chang 6 and Chang 81 and TypeⅡincludes the oil from Chang 82 and Chang 9. Although both of the 2 types of oil come from the source rocks of Chang 7, but the oil maturity parameters such as C2920S/(20S+20R), C29 ββ/(αα+ββ), Pr/Ph and gammacerane index of TypeⅠoil are obviously lowerer than those of TypeⅡ, and the parameters reflecting organic matter source like αααC27 sterane/（C27-29）sterane, 4-methy sterane/regular sterane and Pr/nC17 of TypeⅠoil are slightly higher than those of TypeⅡ. The analysis on hydrocarbon accumulation periods indicates that TypeⅠoil is the mixture of the matured oil generated during the hydrocarbon generation peak and the previously existing low-maturity oil in the source rocks of Chang 7, and TypeⅡoil should be the product of large scaled hydrocarbon charging during the middle of Early Cretaceous