Abstract: As the basic parameters needed in reservoir fracturing stimulation, in-situ stress and fracture pressure will change significantly after a long period of production in fault-block reservoirs. According to the elastic mechanics theory for porous media, the paper analyzes the influences of fault-block reservoir pressure depletion on in-situ stress size and direction, based on which the variations of crack initiation and extension are studied. The results show that fault-block reservoir pressure depletion results in inhomogeneous attenuation of in-situ stress, fracture extension pressure declines linearly during fracturing, fracture extension direction deflects rapidly at the early stage of pressure depletion and relatively slowly at the late stage of pressure depletion; reservoir pressure depletion leads to the linear decline of crack initiation pressure in an open hole. The fracture pressure reduction extent in fault-block reservoirs is larger than that in conventional homogeneous reservoirs after the reservoirs are put into production, and the relationship between fracturing feasibility degree and wellbore trajectory in directional wells changes. For fault-block reservoirs, wellbore trajectory should be designed reasonably according to pressure depletion extent to reduce the difficulties of fracturing operation if fracturing stimulation is needed at the late production stage.