Abstract: Liaohe basin is a rift basin developed in the Mesozoic and Cenozoic. Eastern sag is a segment of Liaohe basin. There were different intensity of volcanic expulsion influenced by Yanshanian and the episodesⅠ、Ⅱ、Ⅲ of Himallayian movement. There were several major types of fractures of the volcanic rock reservoirs:primary fracture and secondary fracture. Primary fracture were formed during the lava crystal and the secondary fracture generated during the volcanic reconstruction by tectonic movement, and wind action, solution. The internal causes of the volcanic rock fracture formation were the rock type, the style of expulsion and the tectonic position; the external causes of the volcanic rock fracture were the tectonic movement, solution and wind action. The superposition of the fracture system in the area caused by the uniting of the internal causes and the external causes. Thereunto, tectonic fracture was the main secondary fracture, the reflection of the stress field accorded with regional or local stress field. The courses of different distinction, different period fault activity were the courses of generating and superposition of the regional or local fracture. The generating of tectonic fracture was tightly relative with Yanshanian and the episodesⅠ、Ⅱ、Ⅲ of Himallayian movement. The development of fracture was the key of the oil and gas pool formation in the area, the effective fractures were tectonic and solutional fractures, the tectonic fracture forecast is the effective means of the forecast fractures before drilling, and the fracture fitted well with pore was the advantage of the development of volcanic oil and gas pool.