Abstract: The present disclosure relates to a bacterium-alga coupled sewage treatment device based on energy recycling and a use method thereof. The device comprises a pretreatment device, a photobioreactor, an alga separation apparatus, a continuous flow bioreactor and a secondary sedimentation tank which are sequentially connected in order, the pretreatment device being connected to a municipal sewage inlet pipe, the photobioreactor being connected to a carbon dioxide gas charging device through a gas filling pipeline, one part of a sludge thickening tank being connected to the secondary sedimentation tank, the other part thereof being connected to remaining sludge of the pretreatment device, carbon dioxide generated from the sludge which flows through the thickening tank and is thermally-hydrolyzed and anaerobically-acidified being connected to the photobioreactor through a gas inlet pipeline, and the alga separation apparatus being further connected to a filter press.