The corrosion kinetics, surface microstructure, and corrosion mechanism of Sn-3.0Ag lead-free solder were investigated using mass-loss method in the temperature range from 283.15 to 323.15 K in polyvinyl chloride fire smoke environment. The results show that the Sn-3.0Ag solder exhibits an increase in mass-loss from (22.09±2.01) to (44.66±1.20) g/m² as the temperature increases from 283.15 to 323.15 K. Moreover, the corrosion kinetics is in accordance with Arrhenius law. The surface corrosion products of Sn-3.0Ag solder show a superposition growth trend. At 283.15 K, the surface of Sn-3.0Ag solder shows significant corrosion products. The corrosion process of Sn-3.0Ag lead-free solder is an electrochemical corrosion. Hydrogen evolution and oxygen abstraction reactions occur in the cathode, and the dissolution of the Sn-rich phase occurs in the anode. The corrosion products are Sn₂₁Cl₁₆(OH)₁₄O₆, SnO₂, and SnO.