Abstract: The development of novel blasting technologies that combine high-efficiency rock fragmentation with green and safe characteristics is crucial for resolving the conflict among environmental protection, safety, and efficiency in resource extraction and infrastructure construction under the “dual-carbon” goals. Liquid oxygen transient expansion rock-breaking technology, featuring a simple system configuration, intrinsic safety, and environmentally benign reaction products, provides a potential solution to this challenge. To clarify the fracturing mechanism of liquid oxygen transient expansion rock-breaking, the expansion principle and equipment are analyzed based on the technical characteristics of the method.By investigating the thermodynamic reaction process inside the borehole, the stress mechanisms acting on the surrounding rock are revealed, and a rock fracture process is proposed that considers the synergistic effects of ultra-low-temperature thermal damage induced by liquid oxygen, stress waves, and high-pressure gas. Based on high-speed schlieren experiments, a three-stage reaction hypothesis is established: excitation and incubation, expansion and failure, and gas release. Through gas composition analysis, a combustion–phase-change proportion calculation method is developed to clarify the reaction characteristics of liquid-oxygen transient expansion.Furthermore, digital image correlation and three-dimensional reconstruction techniques are employed to investigate post-blasting fracture characteristics of the rock mass. The results indicate that under gas-dominated impact loading, no crushed zone is formed; fractures are dominated by tensile failure, with a single preferred propagation direction and no secondary cracks. Safety evaluations show that liquid-oxygen cartridges exhibit relatively high initiation thresholds under electrostatic discharge and open-flame conditions.In engineering applications, owing to its green, environmentally friendly, and intrinsically safe features, this technology is suitable for rock-breaking tasks in multiple scenarios and complex environments. Future research on liquid-oxygen transient expansion rock fracturing should further explore the reaction mechanism from multiple perspectives, establish three-dimensional theoretical models for full-process dynamic crack propagation, conduct multiscale analyses of fractured rock masses, and develop precise in-hole delay initiation techniques, so as to expand the application scenarios of this technology.