That is, inorganic flocculants and organic anions are selected to prepare an aqueous solution, which will produce a compressed electric double layer when added to the wastewater, so that the suspended particles in the wastewater lose stability, and the colloidal particles condense with each other to increase the particles, forming flocs and alum flowers. When the floc grows to a certain volume, it will be separated from the water phase under the action of gravity, thus removing a large number of suspended solids in wastewater and achieving the effect of water treatment. In order to improve the separation effect, coagulant AIDS can be added in a timely and appropriate amount.