In view of the difficulties in formation energy replenishment and failed injection and production by water drive in lowpermeability reservoirs， Shengli Oilfield proposed a water injection technology based on pressure drive for low-permeability reservoirs according to the technical requirements for increasing liquid production and stable oil production in the oilfield. Pressure drive could effectively increase the water injection volume through high-pressure water injection. Field tests showed that a certain scale of fractures was formed in the reservoir during the pressure drive. However， the breakdown pressure and fracture propagation law caused by pressure drive were still unclear. Five pressure drive experiments were carried out using natural sandstone and true triaxial hydraulic fracturing platforms to optimize field construction parameters. The influence of injection rate on breakdown pressure and fracture geometry caused by pressure drive was studied， and that of injection modes on fracture geometry was analyzed. The causes were analyzed using the porous elasticity theory. The experimental results showed that there are both obvious fracture initiation pressure and breakdown pressure during the pressure drive. Fracture development presents three stages： elastic deformation， microfracture development， and instability failure. The fracture initiation pressure is basically unchanged， and the breakdown pressure gradually decreases with the increase in injection rate. The H-F model can be used to predict the fracture initiation pressure， and the H-W model can be used to predict the upper limit of the breakdown pressure. The direction of fracture propagation caused by pressure drive is greatly affected by rock heterogeneity， which affects the pore pressure field near the wellbore and thereby changes the stress field so that the fracture propagation is no longer perpendicular to the minimum geostress. The angles between the branch fracture and the main fracture are large during injection with a constant rate， forming a fishbone-like fracture； the branch fracture is nearly parallel to the main fracture， and the fracture zones are formed on both sides of the main fractures during injection with a variable rates.