Abstract: The unitized regenerative proton exchange membrane fuel cell(URPEMFC) integrates both electrolysis and fuel cell modes. It exhibits advantages such as zero emission, high efficiency, and high energy density, thereby demonstrating broad application prospects in the power supply systems of deep-space probes. A systematic review is conducted on recent research progress in URPEMFCs, encompassing single cells and their components, as well as stack and system integration. Emphasis is placed on the challenges posed by bidirectional requirements on materials, structure, and transport pathways under dual-mode operation. Key challenges identified include the high cost and insufficient stability and activity of catalysts in acidic media; significant performance degradation of the proton exchange membrane(PEM) within the complex electrochemical environment of dual-mode operation; conflicting requirements for water and gas transport in the gas diffusion layer(GDL) and bipolar plates(BPPs), resulting in severely imbalanced transport performance under low-gravity conditions; and a scarcity of full-scale simulation studies, high model complexity, and underdeveloped auxiliary system research at the single-cell and stack levels. Finally, outlooks on key future research directions are presented, aiming to provide a theoretical basis and technical reference for the future development of URPEMFC technology in aerospace energy systems.