Abstract: It can produce tin slag in the process of melting and wave soldering of SnCu and SnAgCu lead-free solders, which affects the fluidity and wettability of solder, and ultimately affects the use of solder.Selecting the market common used lead-free solder products SnCu and SnAgCu, the jet oxidation experiments at 270 ℃were carried out.Through the analysis of original solder composition and phase and element composition of slag after jet oxidation experiment, the effect of impurity elements on the oxidation resistance of lead-free solders was studied.The experimental results show that after the oxidation experiments, aerophilic elements such as Al, Ca, Fe and Si can be enriched in the slag, thus reducing the oxidation resistance of lead-free solder.