With the rapid development of the air transportation，air traffic will become heavier and heavier, establishing air highway is important to alleviate the increasingly serious problem of air traffic congestion. This paper gives a basic concept of air highway and of ramp, using the basic theory of cell transmission model to present an air highway ramp flow control model. By solving this model, the system minimum time, system clearance time, optimal flow distribution of ramp, and so on are obtained. Results of a case study show that this model can meet the modeling demand of air traffic highway ramp flow control, and also can describe the dynamics feature of traffic flow in air highway system.