Ag-9.5Sn (wt/%) and Ag-7.6Sn-0.87In (wt/%) alloy powders were synthesized by atomization. Oxidation kinetics curves of Ag-Sn-In alloy powder, Ag-Sn alloy powder, pure Sn powder and pure Indium powder were obtained by thermo gravimetric analyzer (TGA). The particle size, surface morphology and surface composition of Ag-Sn-In alloy powders before and after oxidation were investigated. The results show that rapid oxidation mass gain process of Ag-Sn-In alloy powders is divided into two periods, and the former is faster than the latter. Minor In addition could promote rapid oxidation mass gain of the first period. Uniform dense oxide film is formed after In and Sn being oxidized, which hinders the second period of rapid oxidation mass gain process.