The lithium element can be precipitated by sodium fluoride slurry in the impurity removal leaching solution of spent lithium batteries after leaching process. Taking the excess ratio of n(F)/n(Li), reaction temperature, stirring speed, reaction time and washing water temperature as reference factors, an investigation has been conducted on the effects of each factor on the recovery of lithium and the loss rate of such elements as nickel, cobalt and manganese. The experimental results show that the optimal combination of n(F)/n(Li) excess ratio is 1.2, with the reaction temperature being 90 ℃, the stirring rate being 300 r/min, the reaction time being 8 h, the washing water temperature being 90 ℃, the recovery of lithium being up to 90.31%, and the loss rate of nickel cobalt manganese being less than 1.50%.