An effective photoelectrochemical sensor is urgently needed for monitoring of the environmental pollution caused by organic wastes. In this work, we report a facile in-situ illumination-assisted process to introduce uniform metal oxide (Bi2O3) nanocrystals of 2-3 nm in sizes on carbon bridged TiO2 nanotube arrays (TiO2NTAs) (Bi2O3/C@TiO2 NTAs), in which the carbon functions as both electron trapping for high efficiency and system integration. The Bi2O3/C@TiO2NTAs thus made exhibit a highly selective photoelectrochemical determination performance, with low background photocurrent (derived from the decomposition of water) and high detection current (derived from the decomposition of organics target). In particular, the current detection of the Bi2O3/C@TiO2NTAs is 3.38 times higher than that of the pristine TiO2 NTAs. To understand the key working principles involved, they are scrutinized by probing into the photoelectrochemical reaction process, including the light absorption, charge separation and transfer, and surface reactions. With the novel Z-scheme heterostructure system being achieved with Bi2O3/C@TiO2 NTAs, the present work demonstrates the potential of metal oxides with uniform size in nanometer range and conductor-bridged strategy in creating Z-scheme hetero-structure system with high photoelectrochemical detection performance for organics.