Accidents in a nuclear power plant are coped with by operators in the main control room (MCR). An analysis of the workload of operators in a MCR after the happening of initiating events is helpful to the alleviation of human errors and to the promotion of training efficiency. This paper establishes a framework of how man is located in a man-machine interface of a nuclear power plant (NPP) as well as a simulation of the man-machine scenario in accidents in NPPs, including the simulation of the operators’ task and cognitive work and the establishment of task analysis. On the basis of the above, a model of the dynamic changes of the operators’ tasks is constructed and a computation of operators’ workload is conducted. Accidents in a nuclear power plant are coped with by operators in the main control room (MCR). An analysis of the workload of operators in a MCR after the happening of initiating events is helpful to the alleviation of human errors and to the promotion of training efficiency. This paper establishes a framework of how man is located in a man-machine interface of a nuclear power plant (NPP) as well as a simulation of the man-machine scenario in accidents in NPPs, including the simulation of operators and cognitive work and the establishment of task analysis. On the basis of the above, a model of the dynamic changes of the operators ’tasks is constructed and a computation of operators’ workload is conducted.