In the present study, radish (Raphanus sativus) was selected as the experimental plant, and the seedlings were treated with single and mixed solution of uranium (U, 50 μmol·L^-1) and cadmium (Cd,10 μmol·L^-1), respectively. The accumulation characteristics of U and Cd in radish seedlings, as well as the biomass, photosynthetic gas exchange parameters and chlorophyll fluorescence characteristics of radish were measured for exploring the biological effects of the single existence of U and its combination with Cd. The results showed that: (1) U and Cd were mainly distributed in the root of radish, which significantly inhibited the growth and root activity of radish seedlings, and the inhibition effect by the U+Cd mixed treatment was more serious than the single treatments. (2) After single U treatment, the contents of chlorophyll a and carotenoids in radish leaves decreased, and the net photosynthetic rate (P_n) decreased by 43.9% compared with the control. Furthermore, the photochemical quenching coefficient (qP) and electron transfer rate (ETR) of the photosystem Ⅱ (PSⅡ) decreased significantly, while the intercellular CO₂ concentration (C_i), dark respiration rate (R_d) and nonphotochemical quenching coefficient (NPQ) increased significantly. Single Cd treatment also significantly reduced the P_n of radish leaves, but had no significant effect on the photosynthetic pigment contents and chlorophyll fluorescence parameters. (3) After being treated with the mixed solution of U and Cd, the content of U in radish was significantly higher than that of single treatment, while the content of Cd showed an opposite trend. Moreover, the biomass, chlorophyll content, photosynthetic gas exchange parameters and chlorophyll fluorescence parameters of seedlings were decreased more than those of single treatment. In conclusion, it was found that after U treatment, the light utilization efficiency and electron transfer rate were significantly inhibited, which resulted in the inhibition of seedling growth. The incorporation of Cd not only enhanced the U absorption efficiency in radish, but also caused more serious toxic to radish plants.