This study was investigated experimental condition which is able to evaluate photocatalytic activity of various commercial TiO₂. The experiments were performed for three representative substances (ethanol, phenol and methylene blue) and four kinds of commercial TiO₂, under the experimental conditions such as pH, reactant concentration, amount of TiO₂, reaction time and UV intensity. The optimum experimental conditions to evaluate photocatalytic activity were as follows : for ethanol, the initial concentration 1000 ppm, initial pH 8, TiO₂ loadings 0.1 wt%, and reaction time 90 minutes: for phenol, the initial concentration 200 ppm, initial pH 8, TiO₂loadings 1 wt%, and reaction time 60 minutes: for methylene blue, the initial concentration 200 ppm, initial pH 4, TiO₂ loadings 0.5 wt%, and reaction time 30 minutes.