Timely and accurate measurement of soil moisture and its fluctuation is of paramount significance in understanding the global water cycle and improving the weather forecast pattern. With the development of GNSS-R technology

the use of GPS signals reflected from the earth has been proposed as an alternative method to remotely sense soil moisture. Inversion model is established from the truth that the reflectivity is a function of soil dielectric constant which relates to the soil moisture. In order to determine soil moisture from collected data by DMR （Delay Mapping Receiver） fleetly

the whole retrieval flow is processed from original reflected data to soil moisture. In this study

a piecewise model is presented between soil dielectric constant and soil moisture. In order to test the feasibility

the SMEX02 experimental data on aircraft platform taken by NASA was used. The result shows the reflected GPS signal is sensitive to the surface soil moisture.