Abstract: The tight oil reservoirs of the Lucaogou formation are widely distributed in the Jimsar sag of Junggar basin, Northwest China. However, the effects of its exploration and development are unstable because the fracture development characteristics and main controlling factors on fractures are not verified. This study aims to clarify the basic characteristics of fractures and study the main controlling factors on fractures. Based on the data analysis of outcrop, core, rock thin section, SEM, image logging and X-ray diffraction, the paper studies the relationships of fractures with mineral brittleness, lithology, total organic carbon content, stratum thickness and sedimentary microfacies. The study results indicate that the development of the fractures in Lucaogou formation is positively correlated with mineral brittleness and TOC content, and negatively correlated with stratum thickness. The influence of sedimentary microfacies on fractures is complex because the factors of mineral brittleness, lithology, TOC content and stratum thickness should be comprehensively considered. Dolomitic sand flat and sand bar are the developed in the shore-lacustrine facies, while distal sand bar and sheet sand are developed in the delta facies, all these microfacies are favorable for fracture development