The invention discloses a sterilizing and precipitating system for water treatment. The sterilizing and precipitating system for water treatment comprises a aeration tower and a precipitation tower, wherein the water outlet end of the aeration tower is communicated with the water inlet end of the precipitation tower through a water outlet and suction pipe; a water suction pump is arranged on the water outlet and suction pipe; the water suction pump can suck aerated water in the aeration tower into the precipitation tower. The sterilizing and precipitating system for water treatment adopts a precipitate passage structure, so that discharge of excessive clean water along with a precipitate is effectively avoided; meanwhile, under the rotational agitation of auger blades in an aeration device, an air bubble group violently rolls in a column passage, so that the contact area between bubbles and a water flow is increased, the fluidity is improved, and thus the dissolution efficiency is improved.