Multi-temporal interferometric synthetic aperture radar (MT-InSAR) technology was applied to process C-band ENVISAT data from 2007 to 2010, X-band TerraSAR-X from 2010 to 2015 and C-band Sentinel-1A from 2016 to 2018 to monitor ground subsidence along the Shanghai maglev zone and velocity maps were plotted. An optimal multi-level network with high coherent points considering both point density and distribution was used to increase the number of coherent points with high precision efficiently. Comparing the data with different wavebands, the relationship between the image resolution along azimuth and range direction and the number of coherent points was analyzed. The experiments have shown that the coherent points along the maglev track are closely related to the range resolution. In addition, the velocity map obtained by MT-InSAR was evaluated using the levelling data. The result shows the maglev track is stable although there are several subsiding troughs near the maglev track.