Spreading behaviors in the reactive Sn–Bi–Cu/Ni system were investigated by the sessile drop method at temperatures ranging from 523K to 673K. Contact angles and the triple line frontier, characterized by the drop base radius R, were recorded dynamically with a high resolution CCD in an Ar–H 2 flow. Equilibrium contact angles between Sn–17Bi–0.5Cu solder and Ni substrate decrease monotonously with the temperature increasing, which are 43.51°, 25.80°, 24.51° and 20.00° at 523K, 573K, 623K and 673K, respectively. Triple line mobility is obtained when calculating the derivative of R. The maximal triple line velocity approximately increases with the temperature by comparison of the four different spreading processes. Double layer intermetallics formed at the Sn–17Bi–0.5Cu/Ni interface are identified by EPMA and EDS analysis, which are (Cu,Ni) 6 Sn 5 adjacent to the solder and Ni 3 Sn 4 adjacent to the Ni substrate, respectively. The intermetallic compounds could effectively enhance the triple line mobility because of reaction product formation at the diffusion frontier.