Abstract: Fractures are developed in the Carboniferous volcanic reservoir of Zhongguai swell in the northwestern margin of Junggar basin. To identify fracture distribution and its influence on hydrocarnon migration and accumulation, the paper studies fracture characteristics and their controlling factors based on the data of core, thin section, logging and lab analysis, and performs comprehensive fracture evaluation by using logging technology, rock failure degree theory and seismic detection. The study shows that the Carboniferous volcanic reservoir in Zhongguai swell is dominated by high-angle structural shear fractures and vertical fractures, both of which are mostly semi-filling or unfilling. The degree of the fracture dvelopment is mainly controlled by lithology, structure location and weathering and leaching, whose azimuth mainly exhibits near EW, NW-SE，NE-SWand SN directions. The fractures in the volcanic reservoir are mainly distributed in the center and eastern slope Zhongguai swell, and District Wuba. Finally, combining hydrocarbon accumulation rules in the volcanic reservoir with the actual exploration, the paper indicates that the middle part of Zhongguai swell and District Wuba should be the favorable target areas for next exploration.