The invention discloses a lead-acid storage battery colloidal electrolyte and a preparation method thereof. The electrolyte consists of the following components: sulfuric acid, silicon dioxide, sodium sulfate, polyacrylamide, sodium polyacrylate, sodium molybdate, calcium molybdate, magnesium molybdate, sodium tungstate, potassium sulfate and deionized water; method steps It is: add potassium sulfate to dilute sulfuric acid to obtain a dilute sulfuric acid mixed solution, then add it to a sodium silicate solution to obtain a silica colloidal suspension solution, and then add sodium molybdate to the fumed silica nanopowder suspension , calcium molybdate, magnesium molybdate and sodium tungstate to obtain nano fumed silica powder suspension solution, and then prepare polyacrylamide solution and sodium polyacrylate solution, and then, first mix silica colloidal suspension solution and nano vapor phase The silicon dioxide powder suspension solution is mixed uniformly, and then polyacrylamide solution and sodium polyacrylate solution are added thereinto to prepare lead-acid battery colloidal electrolyte. It can be widely used in storage batteries with a capacity above 20AH.