The photoelectrochemical oxidation of bovine serum albumin (BSA) at a cadmium sulfide/titanium dioxide (CdS/TiO2) electrode and its influences on the photoelectrocatalytic oxidation of ascorbate (AA) have been investigated by combining a photocatalydc fuel cell. The UV-excited BSA/CdS/TiO2 electrode exhibits direct oxidation peaks related to tryptophan (Trp) and other amino acid residues. The oxidation products of Trp on CdS/TiO2 electrode exhibit a pair of well-defined quinonyl/hydroquinonyl-based redox peaks at the formal potential of 0.025 V (vs. SCE) controlled by surface-confined electrochemical processes. The BSA oxidation photocurrent linearly increases with increasing BSA or O-2 concentration. The AA oxidation is dependent on the UV irradiation, BSA concentration and photoanode materials. An appropriate amount of BSA leads to a 58% increase in the photocurrent response of AA oxidation on the CdS/TiO2 electrode, and a 0.5-fold increase in the maximum power density of the proposed photocatalytic AA/O-2 fuel cell employing palladium(II) porphyrin Pd (II)TCPP (TCPP = meso-tetrakis(4-carboxyphenyl)porphyrin) modified carbon felt cathode. The present results provide a new platform for evaluating the effects of serum albumin on the antioxidative action of AA in the absence and presence of UV irradiation.