Silicon/carbon (Si/C) composite has been proven to be an effective method of enhancing the electrochemical performance of Si-based anodes for lithium-ion batteries (LIBs). However, the practical application of Si/C materials in LIBs is difficult because of the weak interaction between Si and C. In this study, we applied two-step diazotization reactions to modify graphite nanosheets (GNs) and Si nanoparticles (Si NPs), yielding a stable Si–Ar–GNs composite. Owing to aryl (Ar) group bonding, Si NPs were dispersed well on the GNs. The as-prepared Si–Ar–GNs composite delivered an initial reversible capacity of 1174.7 mAh·g−1 at a current density of 100 mAh·g−1. Moreover, capacity remained at 727.3 mAh·g−1 after 100 cycles, showing improved cycling performance. This synthesis strategy can be extended to prepare other Si/C anode materials of LIBs.