This study utilized a unique method to prepare TiO2/Ag composites by operating the pH value of synthesis solution, which causes the opposite charges on the surface between TiO2 and Ag to enhance the combination affinity of TiO2 and Ag due to electron attraction. The results showed that the TiO2/Ag prepared in solution at pH 5.8 was characterized as high TiO2 dispersibility and the optimal combination between TiO2/Ag, due to the opposite surface charges and the greatest difference in zeta potentials between TiO2 and Ag. The prepared TiO2/Ag was utilized to process acetone photodegradation, and the results illustrated that TiO2/Ag prepared in solution at pH 5.8 showed the best performance in photodegrading acetone. With increasing TiO2 coated on Ag in TiO2/Ag, the photodegradation efficiency of acetone was enhanced. In terms of the average efficiency via TiO2 coating amount, 10 wt% was the most optimal efficient proportion of TiO2/Ag for the photodegradation of acetone.