Abstract: The outbreak of the novel coronavirus pneumonia at the end of 2019 imposed severe pressure on the medical system of China. Several Chinese cities began to build temporary hospitals for the centralized treatment of the pneumonia patients. Because the design and construction of the temporary hospital must be completed in 6 to 10 days, only a few hours are allowed for the analysis of the impact of exhausted air on the surrounding environment. To overcome this difficulty, a high-efficiency simulation method for analyzing the impact of exhausted air is proposed in this study. Based on the open-source computational-fluid-dynamics (CFD) software FDS, the proposed method realizes the fast modeling of temporary hospitals, the cloud computing-based CFD computation, and the monitoring and visualization of harmful air. The proposed method provides an efficient tool for the rapid analysis in the design stage of new-built temporary hospitals. A case study of Wuhan Leishenshan Hospital was conducted to demonstrate the application value of the proposed method in the epidemic prevention of the pneumonia.