Galena can be easily weathered under acid rain conditions and causes environmental issues. This process, in nature, is an electrochemical process. In-situ electrochemical technology and surface analysis technology were combined to investigate this weathering process. The experimental results showed galena weathering under simulated acid rain (SAR) could cause an initial increase in Pb2+ ions and a passive S0 film, and the terminal product was SO42-. Increased acidity stimulates galena weathering, and the promotion efficiency was 2208% as the pH of the SAR decreased from 5.2 to 4.2. The presence of pyrite is favourable for galena weathering, and the promotion efficiency was 150% when contained 25% (w %) pyrite. Galena will release out 1.7 g·m-2·y-1 Pb2+ to solution as the pH of acid rain 5.2, and reach to 95.7 g·m-2·y-1 as the pH of acid rain 4.2 plus the galvanic effect of pyrite.