Abstract: Based on the analysis of saturated hydrocarbon chromatography and chromatography-mass spectrometry of crude oil and source rocks, the author studied the geochemical characteristics of source rocks in Kongdian Formation and space corresponding relation of source rocks with reservoirs in Weibei Sag. It indicates that the 2nd member of Kongdian Formation is the important source rock of oil and gas. Of which the upper part, with highest abundance of organic matter and superior quality, is the dominant contributor, and the middle part, with significant different in gammacerane content, ratio of pristine/phytane and maturity, acts as the secondary. Oil-source correlation indicates that both of the crude oil discovered in 1st member of and upper part of the 2nd member of Kongdian Formation were sourced from the source rocks of the upper 2nd member of Kongdian Formation in northern sag, and the crude oil from the middle part of the 2nd member or 3rd member of Kongdian Formation were from the 2nd member of Kongdian Formation of the same sag, whereas the oil generated from the lower part of the 2nd member of Kongdian Formation mainly accumulated near source.