Cu2O micro-nanoparticles have been successfully fabricated at low-temperature. The experimental results show that the Cu2O has excellent decolorization rate for methyl orange (MO) under both non-light and visible conditions. Through analysis, It found that the catalysis of Cu2O is an electron-sensitization process. Under light condition, the nuclear structure tends to regenerate Cu2O, while under non-light condition, it tends to change to CuO. The reaction temperature will affect the morphology of Cu2O. The synergism between different exposed crystal planes makes the potential energy barrier between Cu2O and CuO increased, which improves the stability and catalytic activity.