With rapid development of informatization and digitalization technologies, digital transformation is pushing ahead in industry around the world, especially in nuclear power operation and maintenance. In the full life-cycle digital transformation plan of nuclear power enterprises, the design institute has accumulated a large number of digital design results, such as the three-dimensional model data of nuclear power plants. These 3D models are handed over to the operation organizations to build digital, visual and intelligent operation and maintenance solutions. Without digital models, field staffs have to check the paper procedures and technical data before or even during the on-site inspection and maintenance preparation, however, this is adverse for field work. The application of 3D digital auxiliary tools and platforms can effectively improve management efficiency and reduce potential risks in nuclear power operation and maintenance. This paper proposed a digitalization and visualization method to improve the digital management level, and developed a 3D visual operation management platform for Daya Bay nuclear power plant. With the platform, nuclear power operation organizations could handle the daily maintenance work in an efficient way, so that to improve the operation management level.