A simple microplasma method was used to synthesize cuprous oxide (Cu2O) nanoparticles in NaCl-NaOH-NaNO3 electrolytic system. Microplasma was successfully used as the cathode and copper plate was used as the anode. The Cu2O products are characterized by X-ray powder diffraction (XRD), field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM). The results show that the morphology of Cu2O nanocrystals obtained by this technology is mainly dependent on the electrolytic media, stirring, current density and reaction temperature. The uniform and monodisperse sphere Cu2O nanoparticles with the size about 400 ~ 600 nm can be easily obtained in H2O-ethylene glycol mix-solvent (volume ratio 1:1) and appropriate current density with stirring at room temperature. In addition, the possible mechanism has been reported in the article. And the average energy consumed in producing 1 g Cu2O nanoparticles is 180 kJ. For the flexibility and effectiveness of this microplasma technology, it will have broad application prospects in the realm of nanoscience, energy and environment.