GNSS-R (Global Navigation Satellite System-Reflectometry) can remotely sense Earth’s surface characteristics and retrieve geophysical parameters, e.g., snow depth and soil moisture. However the surface reflectivity interaction and scattering characteristics from GNSS signals are not clear. In this paper, we model the scattering properties and investigate the surface’s reflectivity characteristics interacting with GPS L1 and L2 signals in order to retrieve multipath signals and precisely infer surface characteristics. Furthermore, the effects of snow accumulating and melting together with bare soil and fixed snow depth are studied by GNSS-R. A case study from GPS observations at BAKE site is also presented as well as discussed.