Cerium doped zinc oxide nano-scale particles was prepared by precipitation method, the properties including structure, morphology and composition were characterized by BET, XRD, SEM, ICP-AES, UV-Vis DRS and FT-IR. A new type of internal immersed irradiation photocatalytic degradation mode was proposed, relationship between liquid layer thickness and light transmittance was investigated. Finally, The conditions of photocatalytic degradation of rhodamine B were optimized, and the kinetics and mechanism were studied. Results showed that the optimum doped ratio and calcination temperature were 3%(n:n) and 500℃ for 2h, respectively. Catalyst particles was sphere appearance with an average diameter distribution of 80~100nm, and with BET specific surface area of 12.9m²/g, the content of doped cerium determined by ICP-AES accorded with theoretical value. The enhancement of catalytic activity was mainly due to the increase of light absorption after cerium doping. The shielding effect of suspension suggested a significant attenuation on light transmittance, light attenuation rate of UV₂₅₄ was twice more than that of homogeneous solution when the catalyst concentration was 0.1g/100mL. It was applied to rhodamine B with concentration of 1.0×10^-5mol/L, the degradation rate reached to 92.5% in 70min when UV lamp power was 15W, pH value was 7, 30℃ and catalyst dosage was 0.1g/250mL, and the degradation rate was up to 80% even after 6 recycle, it followed first-order kinetic equation and the reaction rate constant was 0.05min^-1.