Resistivity changes and intermetallic growth after thermal aging of Matter tin-plated copper sheet for current collector in fuel cell were investigated to survey the diffusion of Cu into Sn in interface and surface. The results show that the intermetallic growth and resistivity depended on thermal aging temperature and dwell time. In Sn plate on a Cu substrate, Cu6Sn5(${mu}$) and Cu3Sn(${varepsilon}$) intermetallics layer were formed at plate_{strate interface. Cu6Sn5(${mu}$<}) intermetallics layer gradually changed Cu3Sn(${varepsilon}$). Moreover Cu get through Sn layer and it was diffused in the surface at $200^{circ}C$. On the other hand, only Cu3Sn(${varepsilon}$) intermetallics layer were formed at plate_{strate interface at $300^{circ}C$<}. Consequently, the intermetallics formation, thermal condition and oxidation of surface, causes increase in the resistivity of Tin-plated copper sheet.