Abstract: 3-aminotriethoxysilane (3-APTS) was used to modify Si nanoparticles to improve the utilization rate of Si as an anode in a lithium ion battery. The structure, morphology and Si content were characterized by SEM, TEM, TGA, XRD, FT-IR, Raman spectroscopy. It is found that the 3-APTS-modified Si has a yolk-shell structure. 3-APTS plays an important role in the dispersion of Si nanoparticles and no obvious Si agglomeration is observed after the modification. The modified Si has an excellent electrochemical performance. The reversible capacity is 913 mAh·g^-1 after 50 cycles at a current density of 100 mAh·g^-1, the first coulombic efficiency is 62.9% and the retention capacity is 99.6% after 35 cycles. These values are better than for the unmodified Si whose initial reversible capacity is 652.9 mAh·g^-1 and 541 mAh·g^-1 after 50 cycles. Moreover, the reversible capacity of the modified Si has a capacity of 480 mAh·g^-1 at a high current density of 1 500 mAh·g^-1, indicating an excellent rate capability.