Abstract:The geospace includes upper atmosphere, ionosphere, and magnetosphere. Geospace environmental changes have profoundly affected human life, which may cause space disasters, endanger ground grid safety, and interrupt satellite radio communication. With the support of the Ministry of Science and Technology, the National Natural Science Foundation of China, and the Chinese Academy of Sciences, Beijing National Observatory for Space Environment has established a series of advanced international level instruments to monitor ionosphere, middle and upper atmosphere, and geomagnetic field. New detection modes and diagnostic techniques have been developed to achieve scientific observation of various geospace environment parameters over China. The observation data have been used to reveal geospace regional characteristics and spatial fine structure and changes. The data have also been used to support scientific research and space weather forecast. Based on the observation data, using analysis, modeling, and numerical methods, three most important driving factors on the variability of ionosphere have been systematically studied, which are atmosphere-ionosphere coupling, magnetosphere-ionosphere coupling, and photoionization and photochemical by solar radiation.