In the present work, we prepared two kinds of quantum sized ZnO particles whose size were 3 nm(P1) and 5 nm(P2), respectively, and studied their surface properties with surface photovoltage spectroscopy(SPS) and electric field induced surface photovoltage spectroscopy(EFISPS). The photovoltaic response of the two samples showed opposite dependence on external electric field. And when electric field was applied, the thresholds of photovoltaic response of the two samples were all red shifted. The results showed that the surface properties of P1 were different from those of P2, because of their different preparation process. We assigned that basic zinc acetate structure exist on the surface of P1 sample. While for P2 sample prepared by aging P1, that kind of surface structure disappeared, but the particles might be doped with lithium ions in the aging process. In the present work, we prepared two kinds of quantum sized ZnO particles whose size were 3 nm (P1) and 5 nm (P2), respectively, and studied their surface properties with surface photovoltage spectroscopy (SPS) and electric field induced surface photovoltage spectroscopy The photovoltaic response of the two samples showed opposite dependence on external electric field. And when electric field was applied, the thresholds of photovoltaic response of the two samples were all red shifted. The results showed that the surface properties of P1 were different from those of P2, because of their different preparation process. We assigned that basic zinc acetate structure exist on the surface of P1 sample. While for P2 sample prepared by aging P1, that kind of surface structure disappeared, but the particles might be doped with lithium ions in the aging process.