MFD (Macroscopic Fundamental Diagram) theory expresses a well-defined relation between space-mean flow, density and speed at a network level when congestion is homogeneously distributed. The highest point and the hysteria loop are both considered as the signal that the network is becoming congested and contains more cars than its optimal condition. In this work, we use MFD to analyze the influence of the damage of Shanghai Middle Ring Road. SCATS (Sydney Coordinated Adaptive Traffic System) data is used to draw MFD. It is found that: 1. Though SCATS has only stop-line detection, a stable MFD can still be obtained by substituting the space-mean density by the mean occupancy of lanes which calculated from SCATS DS (degree of saturation) values. 2. As Figure 1 shows, after the broken of Shanghai Middle Ring Road, the area where the alternative paths of broken routes are located has been severely congested at peak hours.