An intriguing self-powered cathodic photoelectrochemical (PEC) microfluidic aptasensor with enhanced cathodic photocurrent response is proposed for sensitive detection of prostate-specific antigen (PSA). The self-powered system is constructed by a cadmium sulfide-sensitized zinc oxide nanorod array (CdS/ZnO NA) as a photoanode with an iodide-doped bismuth oxychloride flower-array (I 0.2 :BiOCI 0.8 ) as a photocathode, which can generate the electrical output under visible light irradiation with no external power supply. In addition, the ptype semiconductor I 0.2 :BiOCI 0.8 with a special internal electric field between the iodide ion layer and the [Bi 2 O 2 ] 2+ layer could increase the cathodic photocurrent response by facilitating the separation of electron/hole pairs under visible light excitation. It is worth noting that dissolved oxygen as an electron acceptor can be reduced by the photogenerated electron to form a superoxide radical ( • O 2 − ) in the self-powered cathodic PEC system. The further enhanced cathodic photocurrent response can be achieved by eliminating • O 2 − that reacts with the luminol anion radical (L •− ) to produce chemiluminescence emission, which serves as an inner excitation light source. What is more exciting is that the integration of the photoanode and the photocathode into a microfluidic chip could realize automatic sample injection and detection. On this basis, the proposed aptasensor presents excellent reproducibility and high sensitivity for detecting PSA and exhibits a good linearity range (50 fg•mL −1 to 50 ng•mL −1 ) with a low detection limit (25.8 fg•mL −1 ), which opens up a new horizon of potential for sensitively detecting other kinds of disease markers.