Abstract: In order to explore the time-varying characteristics of fire parameters such as Carbon Monoxide （CO） concentration， visibility， and fire temperature when a fire occurs， in the report， an old activity center was used as an example， Revit software was used to construct the building physical model， and the Fire Dynamics Simulator （FDS） software Pyrosim was used for the numerical simulation calculation of the three fire conditions. The results showed that under fire conditions， the time for reaching the critical value of the fire CO concentration， visibility， and temperature under closed window conditions are shorter than that under the opened window conditions with 41.3%， 11.8%， and 16.3%， respectively. Compared with opening a window at the fire source， opening a window near the stairwell can effectively reduce the harm. Our data can provide corresponding preventive measures and countermeasures for subsequent fire prevention and emergency management.