Abstract: The characteristics of microwave reflectivity are studied theoretically and experimentally. hmicrowave reflectometer is constructed. Microwave radiation transfer of reflection in the process of near field is studied. Microwave reflectivity of natural ground truth in X-band, for example, water, sand and oil slick on water surface is measured.The experimental resulis are in agree with the theoretical prediction. The characteristics and the application in microwave remote sensing are discussed.