In the present study, a causticization method combined with alkaline leaching and purification process was used to treat with lead refining slag. In the alkaline leaching process, the effects of alkaline concentration, temperature, liquid to solid ratio, leaching time, and agitating speed were investigated, and the optimized leaching conditions were established: 2 mol/L of NaOH concentration, 2 h of leaching time, 85 degrees C of temperature, 6 mL/g of liquid-to-solid ratio, 800 r/min of agitating speed. Under these conditions, the leaching rate of Sn reached 92% while the leaching rate of Pb was about 29%. After a purification process, the concentration of lead in the leachate was reduced to 0.0001 g/L. Finally, high-purity calcium stannate (CaSnO3 center dot 3H(2)O) was obtained from the purified solution by the causticization process under the conditions: 5g of CaO dosage (per 200 mL solution), 85 degrees C of temperature, 2 h of time and 800 r/min of agitating speed. The precipitation rate of Sn was as high as 99.22%.