In order to reduce life loss caused by flood dam-break and effectively organize staff to withdraw from dangerous area, we introduce in detail the technology of flood evacuation route analysis, and discuss the procedures of using GIS-based network analysis technology to calculate flood evacuation routes. These procedures include topological check and manipulation of road network, establishing of digital road network model, optimal matching between transfer unit and evacuation shelter, and optimal calculation of evacuation routes. Then, we take dam-break at the right bank of Hunhe river, located in Liaoning province, as an example. We realize the nearest route searching for evacuation and draw evacuation map. The results show that, GIS network analysis technology is convenient for calculating optimal evacuation route, and can help us increase the efficiency and save cost during evacuation. The flood evacuation map and evacuation method from GIS technology can be references for emergency plans on flood control.