The invention discloses an efficient use method of a cheap environmental-friendly flocculant and belongs to the field of water treatment. The efficient use method comprises the following steps: I, crushing flocculant granules into a powder material less than 200 meshes; II, putting the powder material into water, and performing uniform aeration stirring and mixing by using a micro nano aeration device so as to obtain a saturated solution for later use; III sucking supernate of the saturated solution by using the micro nano aeration device, and uniformly putting the supernate into a liquid to be treated. The flocculant granules used in the method can be one or more of gypsum, granite, silicate powder and porous rock or soil with calcium-magnesium-aluminum components, and together with the micro nano aeration device, defects that in the prior art a flocculant is relatively high in production cost and poor in use effect are overcome, materials can be taken for production on site, the costis greatly reduced, and the purpose of cheap and environmental-friendly water purification is achieved.