Abstract: Based on the core description and three-dimensional finite-element numerical simulation, the authors comprehensively evaluated the distribution characteristics, development rule and effect on exploitation of different fracture groups. There are four group fractures which were controlled by sedimentary microfacies and structure in Daan oil field. Under the effect of modern stress field, the permeability of the EW fracture is the best, then the NW and NE fractures, the NS fracture is the worst. The mudstone partings absorb water seriously and have important influence on exploitation effect because both hig-dip tectonic fracture and low-dip bedding detachment fracture are developed wel1.