When utilizing polarization remote sensing for earth observation, or atmosphere scattering, the polarization effect of atmosphere is always higher than the land surface's. It is usually believed that the polarization effect of the atmosphere is the main information resource of the remote sensing sensor. Thus the land surface's polarization is often ignored in remote sensing retrieval. This conclusion is based on the assumption that the reflection of land objects is diffuse reflection. However, in most cases, land objects are not standard Lambertian. Sometimes the polarization effect of those objects is stronger than the atmosphere's. In this study, the reflection mechanism of the land surface and the interpretation model of polarization spectrum were deduced. Our results show that the imaging spectrum experiment has the land surface polarization effect which can even reach to 50% or more in some cases. The polarization signal of sensor will be greatly affected by the land surface. So the polarization effect of land surface is an important factor which can not be ignored during the study of quantitative remote sensing.