The invention discloses a photosynthetic bioreactor and a method for culturing photosynthetic microorganisms. An annular flow channel (1) is formed in the photosynthetic bioreactor; the bottom of the annular flow channel (1) is provided with a flow-disturbing member (2); and the flow-disturbing member (2) cyclically moves along the annular flow channel (1) under the driving by a driving mechanism so as to drive a nutrient solution in the annular flow channel (1) to flow to the liquid level of the nutrient solution from the bottom of the annular flow channel (1). According to the invention, flowing of the nutrient solution is driven by the motion of the flow-disturbing member, so energy consumption is saved, and better culture effect can be obtained. The reactor for culturing photosynthetic microorganisms is beneficial for large-scale, low-cost and high-efficiency outdoor culturing of photosynthetic microorganisms.