Rapid and sensitive detection of glucose concentrations is very important for human health. Herein, an ultrasensitive photoelectrochemical dual-electron-acceptor biosensor was constructed by modifying the TiO2 nanotubes (NTs) with polydopamine (PDA) and amino-functionalized graphene quantum dots (N-GQDs)/GOx. PDA is grown on the top of the TiO2 NTs by the electropolymerization, and N-GQDs are loaded into the inner of the TiO2 NTs by a microwave-assisted method. The TiO2 NTs/PDA/N-GQD dual-electron-acceptor biosensor exhibited a highly enhanced photoelectric response, excellent electron-hole separation efficiency, low detection limit (0.015 mM), wide linear range (0-11 mM) and ultrahigh sensitivity (13.6 mu A mM(-1) cm(-2)). The prepared biosensor reflected high selectivity and excellent stability. This work also provides new insights into other optoelectronic biosensors.