Surface Photovoltage Spectroscopy (SPS) has been extensively employed in the determination of the energy positions and surface states of ZnO and dye-sensitized ZnO. At room temperature, the energy trapping level E_t1 value of ZnO showed the experimental results of 1.122 eV (λ=1100 nm) by SPS method. In the case of the acid type or the Na salt type dye of triphenylmethanes, the presence of the adsorbed dye on ZnO showed the change of E_t1 value into the E_t2 value of dyed ZnO spectrum which shifted towards a longer wavelength and E_t2 is 0.989 eV (λ =1250 nm). An infrared photovoltage value ( V_IP ) of the acid type dye shows larger V_IP than that of the Na salt type dye due to the high photo-desorption of adsorbed oxygen ion from the ZnO surface. The hydrophilic characteristic of the Na salt type dye seems to responsible for its low V_IP value. The H₂O molecules of moisture seem to act on the recombination center or the trapping center in the zinc oxide surface. Finally, the desensitization of the Na salt type dye for the intrinsic photoresponse of zinc oxide seems to be related and explained by the hydrophilic characteristic of the Na salt type dye.