Abstract: In recent years, theatmospheric layer in the altitude range of about 20-100km iscalled the near space layer by aeronautical and astronauticalcommunities. Owing to rapid developments of technologies andapplications related to this layer, there are more and moredemands on deep understanding of atmospheric environments in thislayer. Scientifically, this layer is called the middle atmosphericconsisting of the stratosphere, mesosphere, and lowerthermosphere, and each of these consecutive layers has its owncharacteristics of atmospheric state, composition and interactionswith solar radiation and particulate activities. Since theatmospheric sounding in this layer is rather difficult, knowledgeabout this layer is relatively weak. In recent decades, moreefforts have been paid to the exploration of this atmosphericlayer by satellite and ground-based remote sensing. In this paper,we will briefly present the basic situation, major controllingfactors and processes, empirical models of this layer, as well asdynamical-physical-chemical modeling and related numericalsimulations. And finally some suggestions for advancing theapplication of near space environment are offered.