Abstract: Porous Ti-6Al-4V alloy exhibits promising application prospects in orthopedic hard tissue repair and replacement, owing to its elastic modulus close to that of human bone tissue, favorable bone ingrowth capacity and excellent biocompatibility. Nevertheless, its high specific surface area, complex pore channel structures and environmental differences between internal and external surfaces result in insufficient surface bioactivity, degraded corrosion resistance, poor antibacterial performance and inadequate long-term service stability, which restrict its clinical applications. As a surface modification technology capable of in-situ fabricating ceramic oxide coatings on titanium alloy surfaces, micro-arc oxidation (MAO) has become an important approach to enhance the surface properties of biomedical porous titanium alloys, due to its advantages including high coating-substrate bonding strength, tunable process parameters, adaptability to substrates with complex morphologies, and easy incorporation of various functional elements. This paper systematically reviews the research progress in surface microstructure and property regulation of biomedical porous Ti-6Al-4V alloy via MAO, and emphatically analyzes its film formation mechanism, structural evolution characteristics and synergistic improvement laws of multiple properties in porous systems. Studies reveal that the MAO process generally undergoes anodic oxidation, spark discharge, micro-arc discharge and arc discharge stages, and coating growth exhibits both inward and outward growth characteristics. The inward growth contributes to the formation of a dense layer tightly bonded to the substrate and improves corrosion resistance, while the outward growth facilitates the construction of a rough porous surface and the incorporation of bioactive components such as Ca and P, thereby enhancing cell adhesion and osseointegration ability. Compared with dense Ti-6Al-4V alloy, porous Ti-6Al-4V alloy possesses uneven pore size distribution, coexistence of interconnected pores and closed pores, and tortuous complex internal pore channels, which complicates local electric field distribution, discharge behavior as well as mass and heat transfer conditions. Consequently, the coating tends to present thickness discrepancy, uneven growth and defect enrichment on internal and external pore surfaces. It can be concluded that the porous structure is not only the foundation for mechanical matching and bone ingrowth, but also a critical factor affecting film quality and surface performance during MAO treatment. In terms of property regulation, MAO can form ceramic oxide layers with crater-like micropores on porous Ti-6Al-4V surfaces. The pore size, roughness and thickness of coatings are significantly affected by voltage, current density, oxidation time and electrolyte composition. Moderate roughness and open pore structure help increase the specific surface area and promote cell adhesion, proliferation and bone tissue ingrowth. However, excessive discharge may cause pore coarsening, surface ablation and microcrack generation, reducing coating density and structural integrity. Meanwhile, although MAO can improve surface hardness, wear resistance and corrosion resistance, and enhance bioactivity and antibacterial performance by introducing Ca, P, Ag, Zn, Cu and other elements, coating defects, residual stresses and coating inhomogeneity may weaken coating-substrate bonding strength and even reduce fatigue life. Particularly for porous implants, fatigue performance better reflects service reliability under long-term cyclic loading, which should be the focus of subsequent research. In general, MAO possesses remarkable advantages in surface functional modification of biomedical porous Ti-6Al-4V alloy, and can realize comprehensive improvement of bioactivity, corrosion resistance and antibacterial performance to a certain extent. Nevertheless, in complex porous systems, critical problems still remain, including insufficient coating uniformity, difficult control of microcracks and residual stresses, challenges in synergistic optimization of multiple properties, and lack of long-term service evaluation. Future research should be further carried out on discharge mechanism, film formation behavior and multi-functional synergistic regulation in complex pore structures. Combined with process optimization, composite modification, structural design and long-term in vitro and in vivo evaluation, efforts should be made to promote the transformation of biomedical porous Ti-6Al-4V alloy from laboratory research to clinical applications.