In this study, the interfacial reactions, microstructures, and intermetallic compounds (IMCs)of 68In–32Bi, 50In–50Bi, and 33In–67Bi (in weight percent)low melting alloys reacted with Cu substrates were investigated. CuIn2, Cu11In9, and Cu2In IMCs formed at the interface in different In–Bi/Cu systems and were characterized by grazing incidence X-ray diffraction (GIXRD)and electron probe X-ray microanalyzer (EPMA). The CuIn2 and Cu11In9 IMCs formed at the interface phase transfer to Cu11In9 when annealing temperature was greater than 70 °C. CALPHAD-type thermodynamic calculations were performed to illustrate the corresponding diffusion paths. Moreover, shear tests were conducted and indicated that 50In–50Bi solder joint provide the highest shear strength among the three alloys.