MXenes, as emerging two-dimensional transition metal carbides/nitrides, have shown considerable potential in multiple fields due to their high electrical conductivity, tunable surface functional groups, and excellent interfacial properties. However, inherent limitations, such as limited band structure modulation, single terminal functionality, and susceptibility to oxidation, hinder their further development in complex application scenarios. Surface modification engineering, which regulates the chemical termination and interfacial microenvironment of MXenes, has become a key strategy to break through these performance boundaries and impart multifunctionality. This review systematically summarizes the latest research advances in surface-modification-driven functionalization of MXenes. It focuses on modification strategies and structural tuning, with particular emphasis on the effects of surface functional group modulation on their electronic structure, interfacial charge distribution, and ion transport behavior. Furthermore, the innovative applications of functionalized MXenes in fields such as optoelectronic detection, electrocatalysis, energy storage, and biomedicine are summarized. Finally, the challenges faced by surface modification are outlined, and prospects for future development toward atomic-level precision control and multifunctional integration are discussed, providing theoretical support and technical guidance for the transition of MXenes from basic research to practical applications.