As a new lithium electrolyte salt,the purity of lithium difluorosulfimide（LiFSI） has great influence on the perfor-mance of lithium ion battery.In order to prepare high-purity LiFSI product,three technological parameters including ratio of material to liquid（mass ratio of crude product to purified solvent）,crystallization time and cooling rate and their interaction effects on the purity of the purified products were systematically studied based on the response surface method,and the rele-vant mathematical prediction model was established.Results showed that under the conditions that the ratio of material to liq-uid was 20.7%,the crystallization time was 30.2 h and the cooling rate was 3.4 ℃/h,the purity of the prepared LiFSI product was 99.98%.