A direct Z-scheme CuSnO3@Cu2O heterojunctions photo-electroactive material were reasonably designed and fabricated by electrodeposited Cu2O on fluoride doped tin oxide (FTO) substrate followed anchoring 3D CuSnO3 microspheres onto Cu2O film. The novel 3D architectures can favor the mass transfer, provide multiple active sites and improve light absorption during the photoelectrocatalytic reactions. The artificial heterogeneous Z-scheme photoelectrochemical (PEC) system further prolong electrons path, promote the separation of photogenerated charge carriers and maintain high redox ability. As expected, the constructed Z-scheme CuSnO3@Cu2O as the photocathode show excellent dual functional properties which can not only detect the trace nitrobenzene (NB) but also undergo catalytic reduction of NB to less toxic species (aniline, AN) under visible light irradiation. Based on CuSnO3@Cu2O photocathode, the photocurrent was linearly proportional to the concentration of NB ranging from 0.5 nmol L-1 to 100 mu mol L-1, and the detection limit (S/N=3) was 0.43 nmol L-1. The fabricated sensor was successfully used to sensing the trace NB in real samples and it showed excellent anti-interference ability, good reproducibility and high stability. Besides, CuSnO3@Cu2O exhibited high PEC activity for NB reduction, 85.70% reduction efficiency was achieved within irradiation for 2.5 h. Thus, this study may provide insights into designing advanced photoeletrocatalysts for energy conversion and render a tunable platform in photoelectrochemistry for the monitor and clean-ups of environmental pollutants.