In summary, Cu2O crystals were grown in one step using the reverse dismutation reaction of Cu2O via a high pressure flux approach for the first time, and the morphology of our as-prepared crystals was shown as truncated octahedra. The mechanism we proposed suggests high pressure was applied to increase the yield and facilitate the growth of Cu2O crystals. The green and facile method for well-controlled synthesis of Cu2O truncated octahedral shape with the active basal facets would find many applications in the chemical industry. This approach also provides a chance of the green-industry production of Cu2O..