In these days, Disaster Management Systems have still put emphasis on its recovery more than the prevention of disaster events. However, the countermeasure of restoration has limitations to prevent the caused loss because the disasters often happen and are massive. Therefore, we propose a disaster prevention system for supporting the safe urban. In this paper, we try to construct a real-time monitoring system to prevent disaster events using new technologies such as Wireless Sensor Networks (WSN) and Geographic Information System (GIS). As a prototype to simulate the fire disasters on real-time, we construct gas sensors and temperature sensors. Our system consists of a WSN system to collect data of the gas and temperature sensors and to monitor the situation information. Our contribution is to provide a prototype application to prevent the disasters from the fire by constructing a WSN system with gas and temperature sensors.