Abstract: Wellbore integrity serves as a critical guarantee for the safe operation of oil and gas wells, and its failure can lead to severe economic losses, environmental risks, and safety incidents. As hydrocarbon exploration and development extend into deep water, deep formation, and unconventional resources, the complex downhole environments characterized by high temperature, high pressure, and strong corrosion impose higher demands on monitoring technologies. Traditional monitoring methods, such as noise logging and cement bond logging, suffer from limitations including limited spatial coverage and poor real-time performance. Distributed Fiber Optic Sensing (DFOS) technology, leveraging its advantages of full-well continuous coverage, high spatio-temporal resolution, immunity to electromagnetic interference, and long-term stability, has emerged as a revolutionary tool for wellbore integrity monitoring. This paper systematically reviews the principles, research and application progress of key DFOS technologies—including Distributed Temperature Sensing (DTS), Distributed Acoustic Sensing (DAS), Distributed Strain Sensing (DSS), and Distributed Temperature and Strain Sensing (DTSS)—in areas such as wellbore leak detection, cement sheath integrity evaluation, casing stress and deformation monitoring, annular pressure and fluid channeling identification. By analyzing representative studies over the past decade, this review summarizes the challenges faced by DFOS technology in terms of adaptability to extreme environments, processing of massive datasets, deployment costs, and technical integration. Furthermore, it outlines future development directions, encompassing intelligent interpretation algorithms, novel sensing materials, multi-technology integration, standardized database establishment, and low-cost operation modes. This review aims to provide theoretical reference and practical guidance for researchers and engineers, promoting the deeper application and innovative development of fiber optic sensing technology in wellbore integrity management.