Aim at the rare and strong subjectivity of evaluation method on regional air route network capacity, this paper puts forward a dynamic capacity evaluation model based on directed graph theory. The model fully extracts the characteristics of air route network which can abstract the complex air route network with multi source and sink into standard air route network with single source and sink, introduces the impedance formula of air route to integrate controller factors into objective capacity assessment and uses the algorithm of FordFulkerson to solve the capacity and critical paths of air route network. Finally, this paper takes a flight information area as an example, analyses the capacity characteristic of the air route network and finds out bottleneck capacity of critical paths is 354.4 sor/h, which prove the accuracy and effectiveness of the model.