Abstract: In order to definitely understand the fracture characteristic and formation period in oolitic dolomite reservoir of Feixianguan No.1 and No.2 members of Lower Triassic in Puguang gas field, this paper presents detailed description and statistical analysis of the fractures of cores and thin?section, including the fractural occurrence, pack density and fracture opening, etc., and discusses the fractural group system and direction using paleomagnetic thin?section orientation technology. It is suggested that the NEE-SWW direction is the advantageous group system, while the fractures of different group systems reflect that the strata may undergo multistage tectonic activities. Based on the fracture cutting limit matching relationship, the iridium content and the filling carbon and oxygen isotopes, it is determined that there exist three periods of fracture formation, such as Late Indosinian period (the secondary formation period), Yanshan period (the major formation period）and Late Yanshan-Himalayan period (the effective fractures major formation period nowadays). Such a study can provide the important geological information for geological modeling and oil?gas accumulation of target zones in this area