The invention discloses a lead-acid storage battery electrolyte and a preparation method therefor. The lead-acid storage battery electrolyte comprises the following components in parts by mass: 50-60 parts of sulfuric acid, 1-5 parts of sodium sulfate, 0.01-0.05 pars of cobaltous acetate, 1-2 parts of fumed silica, 2-3 parts of ammonium persulfate, 0.05-0.15 parts of polyethylene emulsifier, 1-2 parts of glycerine, 3-5 parts of sodium carboxymethylcellulose, 8-10 parts of catalyst and 100 parts of deionized water. The invention also discloses a preparation method for the lead-acid storage battery electrolyte. Sulfuric acid, sodium sulfate, cobaltous acetate, fumed silica, ammonium persulfate, polyethylene emulsifier, glycerine, sodium carboxymethylcellulose, catalyst and deionized water are mixed to obtain the lead-acid storage battery electrolyte. By adoption of the lead-acid storage battery electrolyte and the preparation method therefor, the cycle life of the lead-acid storage battery can be obviously prolonged, the process is simple, and the application can be facilitated.