The invention discloses an efficient composite flocculant preparation method. The preparation method comprises the following steps: choosing argil and diatomite, breaking, grinding, calcining at the high temperature, dissolving in the acid, filtering, separating, dissolving in the acid, mixing, polymerizing, compounding, spraying and drying. An inorganic composite flocculant prepared through the method not only has the advantage of the traditional poly aluminum salt and ferric salt flocculant and the increased molecular weight of the polysilicic acid, improves the flocculation effect, but alsohas the performances of improving the sedimentation velocity and removing the unpleasant smell by introducing the diatomite, and has an excellent water purifying effect and a broad application prospect, meanwhile, the feasible process having a higher additional value is provided for the utilization of the pottery clay, and the purifying effect of the diatomite is utilized to the greatest extent.