The invention discloses a preparation method of lithium difluorophosphate. The preparation method comprises the following steps: adding LiPF6 into a carbonic eater turbid liquid of carbonate at the first heating temperature; reacting to obtain the lithium difluorophosphate (LiPO2F2) at the second heating temperature, wherein the second heating temperature is higher than the first heating temperature. The preparation method provided by the invention has the advantages that the process is simple, the cost is low and the prepared product is high in purity.