Urban geo-environment mainly concerns those regards in and around a city, such as the movement of the Earth crust and the Earth surface, conditions of hydrology, geology, geography and meteorology. Relevant studies on geo-disaster reduction and the influences resulted from human activities on the geo-environment are included as well. The breadth and depth of the influences on the natural system of the Earth primarily depend on how much and how fast the Earth materials are directly and indirectly moved in human activities. It is stressed that another characteristic of megacities is the vulnerability of megacities to disasters and environmental pollution and it will be more aggravative with the expansion and the centralization of a megacity, therefore geo-environmental protection and management are of significant to the city planing and its sustainable development.