Nano TiO2 as a potential photocatalyst has been widely studied for application of environmental decontamination. In this paper, we examine and review the efforts in property improvements by modification, synthesis technique and operation parameter combined with some theory analysis. The effects of the modification by coupling with precious metal and narrow semiconductor, and doping with N, S, and/or C were reviewed. The improvement in synthesis technique includes the increase in amount of doping N, S, and/or C, processing dependence and fabrication of aerogels and nanotubes. The improvement in operation parameter involves approaches to obtain appropriate values of pH, light intensity, H2O2, temperature, catalyst concentration, and initial dyes concentration.