The technology of microwave remote sensing is now experiencing a rapid development never before as microwave remote sensing plays a more and more important role in economic development, environment and disaster monitoring, resource detecting, scientific research and military applications. In this paper, several up to date technologies in microwave remote sensing are discused, such as high performance and new mechanism developing, higher frequency expanding, synthetic measurement using complete electromagnetic band, miniaturization of sensors, and virtual space borne detecting and monitoring. Detailed introductions to 3D imaging radar altimeter, interferometric synthetic radiometer and virtual remote sensing are given. At the last, the authors propose a tentative idea of global topography measurement using small satellite constellation, which can be composed of two satellites, three satellites or four satellites.