Interaction between liquid Sn and 2205 double stainless steel was investigated, and the contamination behavior of low melting point metal Sn on stainless steel was evaluated. The micromorphology of the samples before and after the interaction was observed by metallurgical microscope and scanning electron microscope. The element composition of the samples after the interaction was detected by line scanning and mapping scanning using energy dispersive spectrometer. The stability of passive film in liquid Sn was analyzed by thermodynamic calculation. Then the interaction mechanism between Sn and 2205 stainless steel can be revealed. The results showed that Sn reacted with stainless steel by the formation of FeSn intermetallics for metallurgical bonding. The intermetallics adherency was observed on austenite but ferrite, which was related with the difference on Cr content. The thermodynamic calculation results indicated that Cr2O3 did not react with Sn. Sn contamination had been prevented by the passive film as a physical barrier. On the surface of 2205 double stainless, Sn contamination was caused by the atomic diffusion reaction through the incomplete passive film.