The bismuth-doped CdWO4 single crystals are prepared by the Bridgman method. The absorption spectra, emission spectra and X-Ray photoelectron spectroscopy (XPS) of various parts of as-grown Bi: CdWO4 crystal are investigated. The absorption edge of CdWO4 crystal is red-shifted from 345nm to 399nm due to the introdution of Bi into crystal. The four emission peaks at 470, 528, and 1078 and a weak peak at 1504 nm are observed under the excitation of light beams at 311, 373, 808, and 980 nm. From the X-Ray photoelectron spectroscopic measurements of the Bi: CdWO4 single crystals, Bi2O3 (Bi3+) and NaBiO3 (Bi5+) samples, we infer that there coexit Bi3+ and Bi5+ in Bi: CdWO4 crystals. The fluorescence emissions of visible bands at 470 and 528 nm result from both WO6-6 in Bi: CdWO4 and Bi3+ ions doped in the lattice, while the fluorescence emission of the near infrared band at 1078 nm is due to the Bi5+ luminescence. The analysis result of XPS is consistent with the change of the fluorescence intensity: along the growing direction the emission intensity at 1078 nm and the content of Bi5+ ion both decrease gradually, while the intensity at 528 nm and the number of Bi3+ both increase gradually.