In this work, TiO2 nanoparticles in anatase phase was prepared by sol-gel low temperature method from titanium tetra-isopropoxide (TTIP) as titanium precursor in the presence of acetic acid (AcOH). The effects of synthesis parameters such as AcOH and water ratios, sol formation time, synthesis and calcination temperature on the photocatalytic activity of TiO2 nanoparticles were evaluated. The resulting nanoparticles were characterized by X-ray diffraction, UV–Vis reflectance spectroscopy, transmission electron microscopy and Brunauer–Emmett–Teller techniques. Photocatalytic activity of anatase TiO2 nanoparticles determined in the removal of C. I. Acid Red 27 (AR27) under UV light irradiation. Results indicate that with increasing AcOH/TTIP molar ratio from 1 to 10, sol formation time from 1 to 3 h and synthesis temperature from 0 to 25°C, increases crystallite size of synthesized nanoparticles. It was found that optimal conditions for low temperature preparation of anatase-type TiO2 nanoparticles with high photocatalytic activity were as follows: TTIP:AcOH:water molar ratio 1:1:200, sol formation time 1 h, synthesis temperature 0°C and calcination temperature 450°C.