The metal-free synthesis of graphene on single-crystal silicon substrates, the most common commercial semiconductor, is of paramount significance for many technological applications. In this work, we report the growth of graphene directly on an upside-down placed, single-crystal silicon substrate using metal-free, ambient-pressure chemical vapor deposition. By controlling the growth temperature, in-plane propagation, edge-propaga-tion,and core-propagation,the process of graphene growth on silicon can be identified. This process produces atomi-cally flat monolayer or bilayer graphene domains,concave bilayer graphene domains,and bulging few-layer graphene domains.This work would be a significant step toward the synthesis of large-area and layer-controlled, high-quality graphene on single-crystal silicon substrates.