The scattering coefficient and emissivity are both very sensitive to the moisture content of bare soil surface, which is the essence of measuring soil moisture by using microwave technology. The methods and characters of three microwave remote sensing modes for soil moisture retrieval are discussed in this paper. Firstly, scattering coefficient and emissivity for bare soil surface are calculated based on the theoretical backscattering model BSM. Then the paper analyzes the distribution of isomoisture regions of different data sets, and presents that soil moisture information can be retrieved by using ANN with appropriate input data set.