A series of carbon-doped TiO₂ catalysts was synthesized by hydrothermal method, using titanium isopropoxide and glucose as precursors. Characteristics of catalysts were determined by several methods such as X-ray diffraction, Fourier transform infrared spectroscopy, Brunauer-Emmett-Teller adsorption, UV-Vis diffuse reflectance spectroscopy, scanning electron microscopy, transmission electron microscopy and Raman spectroscopy. Photocatalytic activity of synthesized catalysts was studied in the degradation of cinnamic acid solution. The obtained catalysts have uniform size with dimension of approximately 5 nm. The presence of carbon increases the specific surface area of catalysts, reduces the band gap from 3.26 to 3.05 eV and extends the absorption of the light to the visible region. However, increasing of high glucose contents (5.0 g/L and 10 g/L) in the material leading to decreases the active sites of TiO₂. A sample obtained from glucose solution of concentration 2.5 g/L (TiO₂-C2.5) showed the superior photocatalytic activity under ultraviolet irradiation. The 90 minutes conversion of cinnamic acid (X90) on TiO₂-C2.5, TiO₂-C5.0 and TiO₂-C10.0 catalysts reached 95.3 %, 92.4 % and 90.9 %, respectively. In addition, the photocatalytic activity of TiO₂-C2.5 catalyst was higher than that of TiO₂ (X90 = 91.8 %) and P25 (X90 = 90.8 %) catalysts. Thus, TiO₂-C2.5 sample is expected to be a highly active photocatalyst under visible light irradiation.