Abstract:To study the temporal and spatial variations of Ionospheric Electron Density (IED), the profile distribution of IED over Sichuan during the geomagnetic quiet are inversed by using GPS observation data from Crustal Movement Observation Network of China (CMONOC)and ionospheric tomography technique. The results show that the diurnal variations of IED are obvious at various latitude and altitude. The maximum value of IED appears at 06:00UT. As time goes on, the value of IED gradually decreases and achieves the minimum at 22:00UT. E layer appears in the daytime and disappears in the night. The study demonstrates that the ionospheric tomography (CIT)technique can be used to efficiently monitor temporal and spatial variation of ionospheric structures.