Based on the superposition theorem and elasticity theory,a numerical model for calculating initiation pressure of staged fracturing perforated horizontal well is abstractly presented in this paper.Results indicate that the stress induced by initial fracture is influenced by fracture spacing,and when the initial fracture length is constant,the induced stress along wellbore axis direction decreases gradually until the combined stress field tends to the in-situ stress field.The optimum perforation orientation is in stress condition of this paper is 0°.Induced stress can increase subsequent fractures initiation pressure,and increase with the fracture length.When fracture length is constant,the increase level of initiation pressure decreases rapidly with the increase of fracture spacing.Results from the analytical and numerical models used in this study are interpreted with a particular effort to enlighten the causes of abnormally high treating pressures during hydraulic fracture treatments,as well as engineers study recovery techniques.