NOVELTY - Processing algae slurry pressure filtrate using down-flow aeration biological filter pool comprises e.g. passing the algae slurry pressure filtrate into regulation tank for precipitation, passing through the filter material layer; aerating the bottom of the filter material layer via a roots blower to obtain a biofilm, adding water into biofilm for degradation of algal toxin by bacteria; passing water into the collecting tank and pumping back for back washing; and transferring the algae slurry liquid into a sludge concentrating tank, dehydrating and passing into the regulation tank.    USE - The method is useful for processing algae slurry pressure filtrate using down-flow aeration biological filter pool.    ADVANTAGE - The method synchronously removes chemical oxygen demand, ammonia and microcystin.    DETAILED DESCRIPTION - Processing algae slurry pressure filtrate using down-flow aeration biological filter pool comprises: (i) passing the algae slurry pressure filtrate into regulation tank for precipitation, introducing the obtained liquid into the top of the down-flow aeration biological filter tank via water pump to passes through the filter material layer of the filter tank; where the filter tank is provided with sodium chloride modified clinoptilolite having a particle size of 4-6 mm, and the sodium chloride modified clinoptilolite is obtained by soaking clinoptilolite in sodium chloride solution (0.8 mol/l) at 70-75 degrees C for 2 hours; at the same time aerating the bottom of the filter material layer via a roots blower with a speed of 0.15-0.23 m3/(m2/h) at 15-30 degrees C for 7-14 days to obtain a biofilm and adding water (0.5-1 vol.%) into biofilm for degradation of algal toxin by bacteria (3-6 g/l), where the algae degrading bacteria has a preservation number of CGMCC4498; (ii) passing water into the collecting tank through the bottom of the down-flow aeration biological filter pool, pumping water back into the down-flow aeration biological filter chamber for back washing through a back wash pump, and passing back wash water from the filter pool to the regulation tank through the pipeline; and (iii) transferring the algae slurry liquid of the sludge into a sludge concentrating tank from the regulation tank, inputting the concentrated sludge into centrifuge dehydration decanter for dehydrating, and passing the sewage and concentrated sludge into the regulation tank.