Lead sulfide (PbS) is the main component of galena. The traditional method used to prepare metal lead from galena is disadvantaged by high energy consumption and severe pollution. In this paper, an eco-friendly yet simple process is proposed to prepare high-purity metal lead directly from lead sulfide. According to thermodynamic calculation, lead sulfide can be decomposed into metal lead under vacuum. The pathway to decomposition is based on the reaction of 2PbS (s) = 2 Pb (l) + S₂(g). Besides, an investigation was conducted into the impact of temperature and holding time on the quality of decomposition products and the purity of lead in residue. The investigative results show that the decomposition rate of lead sulfide reached its maximum at 1050 °C for 60 min, which is about 50%, and the purity of the lead in the residue reached 99.51%. When the temperature reached above 1100 °C and the holding time exceeded 40 min, the purity of lead reached as high as 99.81%, but the quality of the residue stayed low. This method contributes a fresh idea to the eco-friendly utilization and efficient purification of galena for preparing high-purity metal lead.