Abstract: The analysis on the organic matter abundance, type, maturity and thickness of the upper source rocks in Cretaceous Yixian Formation of LF-D1 well in Xiushui Basin, northern Liaoning Province, shows that the lacustrine mudstones serve as the main source rocks with wide distribution and large thickness. The TOC of source rocks is 1.37%-8.61%, averagely 3.70%, belonging to medium-good grade. The organic matter types are mainly Ⅱ₁-Ⅱ₂, with high Ro ranging from 1.08 to 1.20, which indicates the thermal evolution reaches mature to oil-generating peak stage with good resources potential.