Nuclear power plants consist of numerous intricate systems that are interconnected and encompass a wide range of equipment and components, such as pumps, valves, containers, and fans. To ensure the safe, stable and reliable operation of nuclear power plants, it is essential to conduct regular maintenance on these systems and their components. To enhance the efficiency of operations and maintenance while minimizing associated challenges and costs, a well-considered operability and maintainability (O&M) design is crucial. This paper explores the application of O&M in the layout design of nuclear power plants, providing a comprehensive analysis from multiple perspectives, including general design principles, specific design methods, and design processes.