Abstract: The in-situ polymerization method was employed to prepare nano-TiO₂/polylactide (PLA) composites with different contents of TiO₂. Scanning electron microscope (SEM) was used to study the dispersion of surfaced-modified nano-TiO₂ in the composites and the results show that nano-TiO₂ dispersed in the PLA evenly when the content of TiO₂ is low ( less than 3wt%). The differential scanning calorimeter (DSC)，thermogravimetry analysis (TGA) and Erichsen test were used to study the thermal and mechanical properties of the composites. The results show that both the thermal and mechanical properties are markedly improved when the content of TiO₂ is 3wt%. It smaximum temperature of heat decomposition T max and the glass transition temperature T g increase by 25.3℃and 4.9℃，respectively，and simultaneously，its tensile strength，elongation at break and Young‘s modulus increase by 83.6%、6.73% and 129.4%.