Photocathode-based sensors possess the advantages of high selectivity and anti-interference in real sample detection，though photocathode produces low photocurrent signal and gives rise to poor sensitivity．Herein，a novel silver bromide-silver-carbon nanotubes（AgBr－Ag－CNTs） composite was synthesized by solvothermal method，and was characterized by scanning electronic microscopy，X-ray diffraction and X-ray photoelectron spectroscopy．Because reduced Ag has revealed localized surface plasmon resonance effect（LSPR），it can amplify light absorption efficiency．Furthermore，CNTs could optimize the electric field near metallic Ag，strengthen light absorption and improve the separation efficiency of photo-generated carriers．Thus AgBr－Ag－CNTs displayed an better cathodic photoelectrochemical activity，compared with AgBr or AgBr－Ag．With K,3,［Fe（CN）,6,］ as photoelectron acceptor，the photocurrent response could be further increased．To develop the practicality of AgBr－Ag－CNTs，an ochratoxin A（OTA） aptasensor was constructed by using AgBr－Ag－CNTs as photocathodic sensing interface，an aptamer as target recognition site，and K,3,［Fe（CN）,6,］ as photoelectron acceptor．Since the aptamer/OTA complex has a rigid structure with weak conductivity，it could effectively block the absorption of light with the sensing interface，inhibit the transfer of photoelectrons toward electron receptors，and reduce the photocurrent signal．Based on the changed photocurrent as signal，the sensor showed a wide linear response from 4.0 pg/mL to 2.5 ng/mL（,r,2,= 0.994） and a low detection limit of 1.5 pg/mL．It was used for detection of OTA in real samples，with recoveries of 92.0%－108%．This work provided a novel photoelectrochemical method for OTA detection，with high sensitivity，specificity and good anti-interference．