Silicon dioxide and potassium carbonate were used as raw materials，water-soluble silicon-potassium fertilizer was prepared by calcining activated silicon dioxide at high temperature.The effects of calcination temperature，calcination time，n（K₂O）/n（SiO₂），and particle size of silicon dioxide on preparation process of water-soluble silicon potassium fertilizer were studied.And the product was characterized by thermogravimetric-differential scanning calorimetry（TG-DSC），X-ray diffraction（XRD） and scanning electron microscope（SEM）.The optimal process conditions were calcination temperature of 900 ℃，calcination time of 30 min，n（K₂O）/n（SiO₂） of 0.85，the average particle size of 160 μm.The silicon-potassium fertilizer prepared under this condition was fully water-soluble with silicon activation rate of 99.34%，effective silicon（SiO₂） content of 39.55 % and K₂O content of 53.23 %.The chemical reaction between silicon dioxide and potassium carbonate at high temperature could inhibit the volatilization of potassium carbonate.The composition of the reaction product may not only contain K₂SiO₃，but also contain K₂Si₂O₅ and K₂Si₄O₉.