A method using a low-temperature Si (LT-Si) buffer layer is developed to grow a SiGe epilayer with low density of dislocations on a Si substrate by molecular-beam epitaxy. In this method, a LT-Si layer is used to release the stress of the SiGe layer. The samples have been investigated by x-ray double-crystal diffraction and transmission electron microscopy. The results indicate that the LT-Si is effective to release the stress and suppress threading dislocations.