An interesting evolution to prepare shape-controlled Cu2O nanocrystals was realized by a convenient one pot synthesis. The Cu2O nanocrystals with different shapes can be obtained simply by adjusting the composition-of reaction system. And, a plausible mechanism was also proposed to explain the nanostructures formation. The surface of Cu2O spheres with thorn exhibited high photocatalytic activity on the degradation of methyl orange (MO) solution under visible light irradiation. The photodegradation efficiency of MO solution reach up to 99.67% at the first 10 min. It is still as high as 98% even at the end of the fourth cycle. (c) 2017 Published by Elsevier B.V.