The ZnO quantum dots (about 3 nm in average size) and the ZnO nanorods (about 80 nm in length and 14 nm in width) were synthesized by the sol-gel method. They were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), UV-vis spectroscopy, and photoluminescence (PL) spectroscopy. The surface photovoltage (SPV) of ZnO nanoparticles was investigated by means of surface photovoltage spectroscopy (SPS) and field-induced surface photovoltage spectroscopy (FISPS), and the bands were identified. The results show that the SPV of ZnO nanoparticles are greatly different for their different sizes as a result of the quantum confinement effect. The ZnO quantum dots exhibit marked quantum confinement properties; that is, FISPS takes a high symmetry in the changes of the response intensity with the strengthening of the two opposed electric fields, and the FISPS response band always appears at about 369 nm, no matter what external electric field is applied. Whereas for the ZnO nanorods an asymmetry in its SPV response under the positive and negative electric field is observed, suggesting the existence of the bound excitons, which appears near the edge of the SPV response band.