The invention provides a sodium/potassium fluosilicate efficient scale inhibitor and a preparation method thereof. The scale inhibitor is prepared by mixing and compounding 100 parts of melamine hexmethanephonic acid and 1-50 parts of OP-10 emulsifier or polyethylene glycol or sodium dodecyl sulfonate. The preparation method comprises the two steps that 1, hexamethylol melamine and phosphorous acid react under the acidic condition according to the mole ratio of 1:(6-10) to prepare melamine hexmethanephonic acid; 2, melamine hexmethanephonic acid and the OP-10 emulsifier or polyethylene glycol or sodium dodecyl sulfonate are mixed to be uniform according to the weight part ratio of 100:(1-50). The scale inhibitor is simple in synthesis process and stable in performance; compared with a traditional scale inhibitor, the scale inhibitor has the advantages of being low in addition amount and low in cost, has an excellent scale inhibiting effect on CaSO4, particularly Na2SiF6(K2SiF6), has a certain scale removing effect on CaCO3 and is wide in application prospect.