Abstract：In the complex system of MeSO4, the removal of Ca2+ and Mg2+ by fluorination precipitation and double salt precipitation deep purification process was studied by single factor method. The experimental results of fluorination precipitation demonstrate that the optimized conditions of fluorination precipitation process are as follows: the excess amount of NH4F is 2.0 times as theoretic consumption, precipitation time 1.0 h, reactive temperature 90℃ and the pH value 3.5. Under these conditions, the average removal rates of Ca2+ and Mg2+ are 92.98% and 89.95%, respectively. The key factors of double salt precipitation process are the excess concentration of (NH4)2SO4 and pH value of the solution. The optimized conditions of double salt precipitation process are as follows: the value of pH is 1.5~2.5, the excess concentration of (NH4)2SO4 2.0~2.5 mol/L, the precipitation time 1.0~1.5 h and the reactive temperature room temperature. Under these optimized conditions, the precipitation rates of main elements of Fe, Mn and Zn are 69.94%, 86.52% and 96.88%, respectively. And the removal rate of Si is 54.85%.