For the problems of evacuation with several exits under the limiting condition of fire smoke and routes capacity, an evacuation model combining of heuristic algorithm and network flow control was established in this study. Taking into account of routes capacity constraints, the aim of emergency evacuation is to minimize the total evacuation time for all people. The optimal evacuation path group, evacuation time and the number of evacuation in the evacuation network can be acquired through updating the evacuation network constantly and finding optimal routes iteratively. An example was presented to show the effectiveness and feasibility of this model and algorithm, and it can be used to explore the method to determine the optimal evacuation plan, while the actual routes inequality was not established.