Amorphous TiO2 coated porous Si (P-Si@a-TiO2) anode material was synthesized by the alloying method and the sol-gel method, using micron-sized Al-Si alloy powder as raw material. The structure and morphology of the materials were characterized by XRD, XPS, SEM and TEM. The preparation mechanism of TiO2 layer and the effect of different coating thickness on the electrochemical properties of the composite were revealed. The results showed that the coralloid porous structure and the appropriate thickness of the coating layer can effectively buffer the volume expansion of the material, and was conducive to improving the stability of the electrode. When the coating thickness was 10 nm, the modification effect was the best. The electrode potential difference of the P-Si@a-TiO2 material was only 0.321 V, after 50 cycles at the current density of 1.0 A/g, the discharge specific capacity reached 1357.4 mA·h/g, showing superior electrochemical performance.