The invention discloses a microbial continuous fermentation system. The microbial continuous fermentation system includes a first fluid, a fermentation tank and an auxiliary device, wherein the delivery pressure and interval duration of the first fluid can be adjusted, an inlet is formed in the side surface of the fermentation tank, and an outlet is formed in the bottom center of the fermentationtank; the first fluid flows in from the inlet, and flows out from the outlet, the auxiliary device is arranged in the fermentation tank, and the axes of the two coincide; the auxiliary device includesa plurality of auxiliary cylinders with different radii and a plurality of luminous elements and bristles which are fixed to the auxiliary cylinders, the auxiliary cylinders are connected sequentially in a sleeved mode, and first inflow mouths which penetrate the thickness parts of the auxiliary cylinders are formed in the auxiliary cylinders; and at least a part of the auxiliary cylinders can rotate around the axis, and the rotational speeds of every two adjacent auxiliary cylinders are different. The fermentation system is suitable for continuous fermentation of microorganisms, the surfacesof cylinder walls can be cleaned through the bristles on the auxiliary cylinders by means of different rotary speeds of the adjacent auxiliary cylinders, and meanwhile, a liquid in the auxiliary cylinders is stirred, so that aggregation and precipitation of the microorganisms are reduced, and uniform exposure of the microorganisms to light is promoted, and reproduction of the microorganisms is promoted.