Abstract: The Chang - 8 formation reservoir of mid Baima area in Xifeng oilfield is low porous and low permeable reservoir. The field production mainly adopts advancing water injection and fracturing, which caused subtle fractures open. On one hand, the open of concealed fractures plays the role of oil and gas migration channel; on the other hand, it can make the injected water fluid channeling a-long the fractures, which caused water flooding. This paper tries to identify the fracture segment based on the research on stress field background, core developing characteristics and special logging response characteristics. According to the change between deep and shallow inductivity of the conventional logging series and the test result, this paper quantitatively interprets the fracture rate of some wells in mid Baima area, analyzes the sudden water flooding wells and the direction of water flooding based on dynamic materials, and points out the direction of water flooding is from the low to high as a rule of sudden water flooding well induced by fractures.