Abstract: Surface soil moisture is an important parameter in draught monitoring and crop yield estimation, it is important to obtain spatial-temporal soil moisture information in large range. Microwave signal is much related to dielectric constant of object observed, and soil dielectric constant is determined by soil moisture, which was the basis of the use of microwave remote sensing technology for soil moisture monitoring. To solve the transformation of soil moisture and soil dielectric constant, the Dobson semi-empirical model was used to build a simulated database, and then the Hallikainen formula calibrated by the least square regression method at radiometer SMOS(1.4 GHz), AMSR-E(6.9 GHz), and scatterometer ERS-WCS and METOP-ASCAT (both at 5.3 GHz) frequency-points were performed to set up the simplified models to transform the real part of the dielectric constant to the soil volumetric moisture content. The validations were performed using both simulated data of the Dobson model and in-situ observations, and the results showed that the simplified models had good accuracy and practicability.