Abstract: Based on the theoretical calculation of hydraulic fracturing initiation pressure and direction, the influence of initial fissure and ground stress on the crack initiation and expanding of hydraulic fracturing is investigated by the stress-seepage coupled simulation method. The variation trend of initiation pressure and direction with the lateral pressure coefficient is obtained. The initiation pressure and direction of the models without pre-set crack and with preseting crack are comparatively analyzed, and the critical stress of initial crack swing of with presetting crack model is discussed. In the end, the effect theory of in-situ stress and original defect to the hydraulic fracturing initiation is elaborated by stress analysis.