Initialization of soil moisture is a very important problem in numerical weather prediction models. In this study, we evaluate the role of soil moisture in land surface processes by SiBUC model. We carried out several kinds of numerical simulations by using same atmospheric forcing and changing the initial value of the soil moisture.The key factor that controls heat balance is a relative humidity of soil surface (fh) for bare soil case, and matric potential in rooting zone (ψ2) for vegetation case. And these two variables change so rapidly in narrow and different range of soil moisture depending on soil type, which leads to complicated reaction of land surface heat budget to soil moisture.