Preparation method of KFSI

The invention relates to the field of organic synthesis, in particular to a preparation method of KFSI. The preparation method of KFSI provided by the invention comprises the following steps: making HClSI and KHF2 to react in the presence of a catalyst, thus obtaining KFSI. Compared with the traditional process, the preparation method of KFSI provided by the invention is simpler in reaction steps, safe, free of pollution and reasonable in preparation cost, effectively controls the introduction of water in the product because of the use of an anhydrous reaction, and further is stable in quality and suitable for large-scale industrialized production.