The invention relates to a photocatalysis and constructed wetland composite fuel cell and a sewage treatment method. The invention aims to provide a photocatalysis and constructed wetland composite fuel cell and a sewage treatment method, which take wastewater as fuel to produce electric energy and realize synchronous operation of wastewater treatment and power generation. According to the technical scheme, the photocatalysis and constructed wetland composite fuel cell is characterized in that the photocatalysis and constructed wetland composite fuel cell is provided with a photo-anode chamberand a constructed wetland fuel cell reaction chamber, and a water outlet of the photo-anode chamber is communicated with a water inlet of the constructed wetland fuel cell reaction chamber; a photocatalytic anode is arranged in the photo-anode chamber; a light source capable of enabling the photocatalytic anode to perform a photocatalytic reaction by emitted light energy is arranged outside the photo-anode chamber; and a light-transmitting part capable of enabling light emitted by the light source to enter the photo-anode chamber is arranged on the photo-anode chamber. The method is suitablefor the technical field of sewage treatment.