Another industrial method is the reduction of copper sulfate (CuSO4) by glucose (Glc), in which the residual of sulfate radical pollutes the water [17]. In both of the above two methods, there are hazardous organic materials or sulfur-substance in the aqueous solution, and the basic raw materials and the additives are complex, consumptive and non-reproducible. In addition, high-temperature sintering method also is commonly used in the industrial production of Cu2O. However the products obtained by this way are easy to harden after sintering, difficult to spread and the purity is not high enough. The costs of this method are high energy consumption and heavy pollution. Due to the desire for environmentally friendly processes, new “green” synthesis is developed for Cu2O crystal growth. Compared to the above methods, our flux approach is the most suitable method for this desire.