Abstract: To study poly (lactic acid) (PLA) /rutile type titanium dioxide (PLA/R-TiO₂) composite anti ultraviolet aging behavior, and reveal the R-TiO₂ scattering the anti-aging mechanism of ultraviolet light, PLA/ R-TiO₂ composites were prepared by melt blending method. By means of differential scanning calorimetry (DSC), X-ray diffraction (XRD), total reflection infrared spectroscopy (ATR-FTIR), mechanical properties test and scanning electron microscopy (SEM), the changes of structure and properties of PLA irradiated by ultraviolet light and the role of R-TiO₂ in improving the ultraviolet resistance of PLA were studied.The changes of surface functional groups of PLA were tested to clarify the changes of structure and properties of PLA.The anti-aging mechanism of R-titanium dioxide scattering ultraviolet light was revealed.Introduction of R-TiO₂ could promote PLA crystallization from 12.11% to 25.91%. With the extension of aging time, the tensile strength of PLA has fallen by 94.5%, and the color difference value increased to 4.13.As result, the surface structures appeared cracks and holes phenomenon. With the R-TiO₂ dosage increased, compared with PLA, the decrease trend of tensile strength after ultraviolet aging became significantly slower, and the color difference value decreased. When the R-TiO₂ added to 3wt%, the UV stability of PLA could be effectively improved.