;Major disasters and accidents occur frequently in recent years, and in all sorts of disasters and accidents, fires of different scale occur almost every day. When a fire occurs, it tends to cause inestimable casualties and loss of property due to three major characteristics of fires: growth, uncertainty, andsporadicity. From the official statistical data, we can discover the top five types of fire disasters, which occur most frequently in a descending order, are building fires, vehicle fires, others, forest and field fires, and marine fires. Through the reviewing of related literatures and use of Fire Dynamics Simulator (FDS), this research analyzes two cases of building fires in Taoyuan City, refers to expertise reports on the causes of fires to simulate and rebuild the fire scenes, and then obtains the data of fire hazard factors including the situations of fires and smokes, temperature, gas concentration, and radiant heat variation. This study also examines the location of corpses, the reasons why the corpses were there, and the relevant information to discuss the causes of death and injury in the two cases,and then offers the suggestions of prevention and improvement. The results of the simulation and rebuilding were mostly consistent with the actual situations and the fire scene investigation results. The improvement of the simulation results can also greatly reduce the fire hazard factors. With all these research results aim to prevent building fires, reduction the number of building fires and casualties can be achieved through good practice.