Occupant evacuation during a building fire is a complex system that includes several highly coupled subsystems, such as building characteristics, occupant characteristics, fire behavior, and evacuation behavior. To study the interaction mechanism between these subsystems to maximize occupant safety during fire evacuation in a building, a multifactor dynamic coupled model based on the Fire Dynamic Simulator and floor field cellular automata model for occupant evacuation in a fire was established. In the model, the dynamic impact of smoke diffusion on occupant movement direction and speed, decrease in occupant health points caused by smoke and trampling, and changes in occupant exit choices in the presence of closed exits were considered in detail. The catastrophic fire accident in the Friendship Palace of Karamay, Xinjiang, China, in 1994 was used as the analysis case, in which the spatial model of the Friendship Palace was reconstructed according to real data and architectural design methods. The safety exits open or closed, radius Rtra, possibility of information transmission Psuc, and wait time twait were discussed to study the influence of these parameters on the evacuation process and results. The study shows that the model could reproduce a fire accident well with Rtra = 4, Psuc = 0.5, and twait = 30. The closed exits increased evacuation time by over 120.3 % and resulted in 439 deaths. These conclusions are important for providing better estimates, guiding architectural designs, and enhancing building safety management.