In this work, a facile electrochemical route i.e., anodic dissolution of bulk Cu at 2.0V or more (vs. SCE) in a NaOH solution containing NH2OH·HCl, was introduced for the synthesis of clean Cu2O microcrystals (Cu2O MCs) with morphologies of octahedron, half circular plate, etc. The bulk Cu electrode can be facilely dispersed into Cu(OH)4 2− in alkaline solutions with the help of intense O2 releasing. In the presence of reductive NH2OH·HCl, Cu(II) was quickly reduced to Cu(I). Due to the concentration gradient of Cu(I) and OH− resulting from the electrochemical reaction and the selective adsorption of OH− on different crystal facets, half circular plate Cu2O MCs were for the first time, synthesized. By changing the NaOH concentration or applied potential, octahedron and rectangular plate Cu2O MCs could also be obtained. Scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD) techniques, etc. were used to characterize the oxides. The Cu2O MCs were phase-pure cubic Cu2O. This electrochemical route is simple, basically green and can be used to synthesize Cu2O MCs with different morphologies.