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• Co 3 O 4 -Au polyhedron as mimic peroxidase and electronic extinguisher for amplify signal response. • TiO 2 /Bi 2 S 3 heterostructure with high photoelectric conversion efficiency. • Cascade enzyme-assisted cycling process for miRNA detection to improve the sensitivity. A photoelectrochemical (PEC) biosensor was constructed based on cascade enzyme-assisted cycling process and Co 3 O 4 -Au polyhedron for miRNA-141 detection. The biotin-modified DNA was immobilized on ITO/TiO 2 /Bi 2 S 3 to link streptomycin-modified Co 3 O 4 -Au through the specific interaction between streptavidin and biotin. The Co 3 O 4 -Au with the competitive consumption effect of electron donor and excitation light energy could effectively reduce the photocurrent signal. Additionally, Co 3 O 4 -Au as peroxidase mimetics enzyme could catalyze the formation of benzo-4-chlorohexanedione (4-CD) precipitate on the electrode surface, which could efficiently prevent electron transfer and decrease the photocurrent signal of PEC biosensor. In the cascade enzyme-assisted cycling process, a small amount of miRNA-141 triggered the double-strand specific endonucleases-assisted cycling process, which could generate DNA fragment for next step experiment. Then the biotin-modified DNA was decomposed by Exonuclease III (Exo III) in the Exo III-assisted cycling process, resulting in the separation of biotin from the electrode surface and the reduction in the loading of streptomycin-modified Co 3 O 4 -Au. The fabricated PEC biosensor with a wide linear range and a low detection limit has potential applications in highly accurate and ultrasensitive monitoring of bioanalysis and disease diagnostics. [ABSTRACT FROM AUTHOR]