Abstract: The decomposition and coordination methods applied to large system design are used for coordinated ramp metering on freeways. The finite-difference model to describe the evolution of the traffic flow on freeways is built. In conjunction with the characteristics of traffic systems, a modified multilayer control method is proposed. There are three control layers in this control architecture: the local control layer to adjust the ramp metering rate, the coordinated control layer to determine the desired traffic density for the local control layer and the self-adaptive layer to select the traffic model and tune its parameters based on the freeway traffic characteristics in real time. Simulation results show that the control system is of good dynamic performance. It can eliminate traffic jams, maintain traffic flow stability, improve passing capability, and make vehicles travel more efficiently and safely.