Green synthesis of nanoparticles using plant extracts is a new method to develop environmentally safe nanoparticles, which can be used in numerous applications. In this study, TiO2 nanoparticles were synthesized from tetra-n-butyl orthotitanate using the vegetal surface active substances extracted from Glycyrrhiza glabra plant via sol-gel method. The synthesized nanoparticles were characterized using X-ray diffraction (XRD), UV-vis diffuse reflectance spectroscopy (UV/DRS), and Fourier-transform infrared spectroscopy (FT-IR). The morphology of the TiO2 powder was characterized using transmission electron microscopy (TEM) and the results indicated that TiO2 particles were nanospheres with a diameter of 60-70 nm. The photocatalytic activity of titania was investigated using the photodegradation of methylene blue, and acid red 88 and coumarin 30 solutions under UV irradiation. The results indicated that the photocatalytic activity of the TiO2 nanoparticles that was carried out by the degradation of MB solution was higher than AR 88 and coumarin 30. Moreover, the same photocatalytic effects on different dyes was not observed for the same size titania nanoparticles.