To enhance the utilization ratio of silicon from potassium feldspar in the hydrothermal synthesis process of kaliophilite and address the issue of alkaline waste liquid produced by this process, this research carried out the filtrate recycling experiment in the hydrothermal synthesis system of potassium feldspar to kaliophilite. The effects of reaction time, reaction temperature, the molar ratio of SiO₂ to Al(OH)₃ and alkali concentration on Si utilization and product structure were discussed, as well as by investigating the reaction process. The effect of the number of cycles on the utilization ratio of silicon, the structure of the product and the stability of the process were investigated by the circulating experiment of the filtrate under the optimal conditions. The reaction mechanism was further explored and the process before and after the improvement was compared. The results demonstrate that when the reaction time was 4.0 h, the reaction temperature was 280℃, the molar ratio of SiO₂ to Al(OH)₃ was 0.8, and the alkali concentration was 12 mol/L, the utilization ratio of silicon in potassium feldspar could attain 94.2%, representing an increase of 60% compared to the process was improved. The product kaliophilite was homogeneous, superior quality and the recycling process was stable.