A method to grow high-quality SiGe graded buffer layer is presented. The main concept of the method is to use Sb as a surfactant when growing Sice graded layers. Compared with a Si0.5Ge0.5 graded sample without Sb surfactant, the Sb-assisted Si0.5Ge0.5 graded layer has much smoother surface and a significantly lower threading dislocation density. Thermal conductivity of a symmetrically strained Si/Ge superlattice grown on Sb-assisted Si0.5Ge0.5 graded layer is also presented.