Fracturing completion technology is an effective method of increasing the production of oil wells in the production and development of low-permeability oil fields. Due to the irregular opening and closing of fractures caused by high-pressure or continuous water injection in the oil field， water flooding usually occurs in the direction of the oil wells， which affects the production of the oil field. Well testing method achieves the connectivity between oil and water wells by short-term adjustments in well production condition which results in well pressure and production change. This article summarizes the causes of dynamic fractures in low-permeability oil fields during water injection. Quantitatively evaluate the connectivity between oil and water wells by using well testing methods. Control the connectivity of fracture between oil and water wells and improving the effect of water injection by optimizing the unstable water injection.