The digitalization and intelligence of nuclear fuel reprocessing plant are gradually being constructed, and the virtual Distributed Control System (DCS) plays an important role to achieve the digital and intelligent transformation. Based on the real DCS in nuclear fuel reprocessing plant, the design method for emulation controller key function of virtual DCS is researched through analyzing the special requirements of virtual DCS compared with real DCS, including DCS level 1 workflow, emulation controller and management software for it, malfunction, simulation control command response and time management. The key indexes of the designed emulation controller are tested and verified using the actual project data. The results show that the relevant functions and performance of the emulation controller can meet those of the real DCS controller, and has a high degree of physical fidelity. Based on the research results, the design and verification of the control logic algorithm of the nuclear fuel reprocessing plant phase II are completed. In the absence of a real control cabinet, part of the factory test activities was carried out in advance, therefore the execution efficiency of the project is improved. The achievement has been applied successfully in a large scale project. The research results provide a certain basis for the construction of large digital and intelligent nuclear fuel reprocessing plants.