Abstract: In the experiments of secondary ion emission on iron-based, copper-based and titaniumbased alloy surfaces exposed to oxygen, we found that, when positive secondary ion yields of metallic elements enhanced with increasing oxygen pressure in the chamber, the oxygn enhancement of ion yield for a element with higher electronegativity was larger ! the secondary ion yields of some elements, such as Cu, Zn and Ag etc. , did not reach to saturated state under our experimental conditions; and there was a linear relation between the yield of positive metallic ions and that of negative oxygen ions during changing oxygen pressure. These experimental results wilt be significance to develop a model named "combined LTE-Bond Breaking" and to improve the quantitative SIMS analysis.