Abstract: Sn-3.0Ag-0.5Cu (SAC305) alloy was prepared by using refined tin with purity of 99.9%. The surface enrichment behavior of trace Zn in oxidation process of refined tin and Sn-3.0Ag-0.5Cu alloy was studied. The dynamic oxidation tests of refined tin and SAC305 were carried out at 300℃respectively.The results show that the slag percentage of SAC305 is lower than that of refined tin.The surface oxidation of refined tin and SAC305 after static oxidation at 300 ℃was studied by XPS depth analysis. The results show that the concentration of Zn on the surface of oxidized refined tin and SAC305 is more than 1000 times than that of the raw material, and SAC305 has higher concentration of Zn element and thinner oxide layer thickness than the refined tin surface. In conclusion, it is considered that high concentration of trace element Zn on the surface of refined tin material can affect the oxidation behavior of tin and tin alloy. It should be paid attention to Zn in the raw material when preparing tin-based alloy solder.