Sn-37Pb solder alloys doped Ni, Al and Cr separately were prepared, and the effect of trace doped elements on the surface film structure of Sn-Pb liquid solder alloys was studied by X-ray photoelectron spectroscopy (XPS). The results showed that the surface of Sn-37Pb liquid alloys was mainly SnO2 and PbO after oxidizing and laying for five minutes at 250°C, and the enrichment of trace Al and Cr was on alloy surface, but the enrichment of trace element Ni was not obvious. The surface oxidation film of Sn-Pb liquid solder alloys was become denser after adding 0.05wt% Ni or Al, which will reduce the growth rate of oxidation film. The thickness of oxidation film was only one-fifth of its original under experimental conditions. However, the oxidation film was become looser after adding trace 0.05wt% Cr, the growth rate was accelerated, and the thickness of oxidation film was increased to two times of its original. Trace Ni and Al were characterized with selective oxidation on Sn-37Pb alloys surface.