Deep and ultra-deep carbonate oil and gas reservoirs, with their vast reserves and immense potential, have emerged as critical strategic assets in global energy supply. However, the complex challenges posed by high-temperature, high-pressure environments, intricate pore-throat structures, and the coexistence of macro-pores, dissolution cavities, and fractures make traditional exploration and production technologies insufficient to manage such complexity. As exploration and development progress, precise reservoir characterization and seepage behavior research face significant hurdles, including advanced modeling, complex seepage experiments, and accurate description of reservoir properties. Therefore, this review offers an in-depth analysis of the latest developments and key challenges in the characterization and seepage behavior of deep and ultra-deep carbonate reservoirs. It provides a comprehensive summary of cutting?edge methods for detailed microstructural reservoir characterization and multi?attribute seismic interpretation techniques enhanced by artificial intelligence. The paper also explores the application and success of multi?scale characterization approaches in complex reservoirs,while outlining the primary technical strategies and emerging trends in reservoir identification and description. Additionally,the article emphasizes recent advancements in understanding seepage characteristics under high-temperature and high?pressure conditions in deep carbonate reservoirs, focusing on multi-scale seepage theory and gas-water two?phase flow mechanisms. By examining experimental data and theoretical models from both domestic and international research, the review highlights current challenges and future directions in seepage studies, providing valuable insights for the development and efficient exploitation of deep and ultra?deep oil and gas reservoirs.