We have synthesized two types of Cu2O samples with size about 700 nm by a facile reduction route. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) and surface photovoltage spectroscopy (SPS). It is noteworthy that one sample prepared using polyethylene glycol (PEG) as template is oxidized in air, but the other one prepared using glucose as template is stable in air. The testing results demonstrate that the difference of nanosized Cu2O morphology greatly affects its stability. In addition, we analyzed the effect of surface oxidation on the SPV signal of the two samples