Aiming at the problems of decreased injection volume caused by pollution of water injection wells in offshore oil fields, shortened effective period of acidizing injection, and low injection pressure of water injection pumps, this study integrates rock dilatancy with high-pressure water injection to propose a fatigue damage-based pulsed high-pressure dilatancy-enhanced injection technology, with comprehensive feasibility investigations and field applications conducted. By utilizing the principle of rock expansion, pulsed high-pressure water injection is carried out to generate two types of microcracks, namely tensile fractures and shear fractures, through shear sliding and pressure expansion of crystals inside the reservoir rock. The mechanism of microcrack expansion under pulsed high-pressure expansion is revealed through true triaxial rock mechanics and CT scanning experiments based on rock fatigue damage. The application of two difficult wells on site shows that the visual water absorption index has increased by 3.25 times and 2.54 times respectively, and the effective period of the measures has been extended by at least 166%. This technology has the advantages of low cost, no movement of the pipe column, no change to the existing offshore platform water injection facilities, large processing radius, and long effective period, making it a new type of injection enhancement technology. This can provide a new idea for the optimal selection of injection technology for domestic and foreign oil field water injection wells.