The spatial distribution and seasonal change of soil moisture are key parameter in numerous environmental studies at both regional and global scales including hydrologic, ecologic, climate change and agriculture. However natural variability and the complexity of the vegetation canopy and surface roughness significantly affect the sensitivity of backscatter from soil. This study we shows the new method to estimate surface soil moisture in high density vegetated area in Taisetsu Mountain of Hokkaido, Japan with an L-band dual-polarization (HH and HH) radiometer measurements. For high dense vegetated surfaces, we use the seasonal multi-temporal backscatter coefficient data and subtraction methods to provide the estimation of the vegetation effects. After the soil moisture corrected based on vegetation phenology, the surface soil moisture can be inferred by the estimated surface backscatter signals.