The geometrical structures of Tin and TinLa（n=1—7） clusters are optimized by using density functional theory（B3LYP） and LANL2DZ basis sets, and the vibrational frequency and electronic properties are calculated. The effect of La atom on the pure Tin clusters is discussed by analyzing the changes of average bond length, binding energy, HOMO-LUMO gaps, and magnetic moments between TinLa and Tin clusters. Furthermore, the reason of the changes caused by La atom is also studied.