This experiment aimed to improve the antibacterial activities of TiO2 by loading the noble metal Pt on its surface. Pt/TiO2 photocatalysts were prepared by photodeposition. X-ray diffraction technology (XRD), UV-visible diffuse reflectance spectra and transmission electron microscopy (TEM) were used to characterize photocatalysts. TiO2 was the mixture of rutile and anatase crystals. Intensity of light adsorption for TiO2 was increased dramatically after Pt loading. Antibacterial activities of noble metal loaded and non-loaded photocatalysts to inhibit reproduction of Escherichia coli under UV irradiation were studied by solution oscillation method. Under irradiation, the bacterial inhibition rate was 45% for TiO2 and 60% for TiO2 with 10% Pt, indicating that the bacterial inhibition rate of TiO2 loaded with 10% Pt was increased by 15% . The results showed that TiO2 possessed antibacterial activity to inhibit reproduction of Escherichia coli. After Pt particles were loaded on TiO2, photogenerated electrons were enriched on the surface of Pt due to the lower chemical potential of Pt. The probability of recombination of photogenerated electrons and photogenerated holes was reduced. More photogenerated holes were free, therefore, the antibacterial activity of Pt/TiO2 was improved.