The sewage is lifted into the pipeline mixer through the water pump, and the flocculant (PAC/PAM) is added to the pipeline mixer through the dosing device, and the agent and the raw water enter the high-concentration flocculation reaction chamber of the automatic water purifier after contact reaction in the pipeline mixer, so that the suspended impurities, colloidal particles and some microorganisms and bacteria in the water are unstable under the action of the coagulant and form a large floc – “alum flower”, and the alum flower rises into the inclined tube sedimentation area, and the flow rate decreases under the action of the inclined pipe, so that the alum flower sinks and the water flow rises. In order to achieve slurry water separation, sinking alum flowers is a good adsorption function, can adsorb the rising alum flowers in the water, one piece down, so as to reduce the load of the rear stage. After precipitation through the inclined tube, most of the suspended matter and colloidal particles in the water have been removed. The water precipitated by the inclined pipe rises to the clear water area and rises to the high-level water tank through the collection weir collection, and is evenly distributed to each filtration area in the filtration area through the high-level water tank, and the suspended solids, colloids and other impurities in the water are further removed, so as to meet the water requirements.