The dissolution behavior of the Ni or Ni3Sn4 phase in molten Sn, Sn-3.0Ag-0.5Cu (SAC), Sn-0.7Cu, Sn-58Bi (SB) and Sn-9Zn (SZ) at 240, 270 and 300oC was investigated in this study. The experimental results show the dissolution rate of Ni in the molten solders follows the order Sn> SAC> SC> SB> SZ. The dense and thick Ni5(Zn,Sn)21 phase was formed at the SZ/Ni interface and could restrain the Ni atoms to dissolve into the molten SZ. Dissolution rate of Ni3Sn4 phase in the molten solders follows the order Sn > SAC> SC > SB at 240 oC, and SC> Sn> SAC> SB at 300oC. Massive spalling of the (Cu, Ni)6Sn5 phase was observed in the SAC/Ni3Sn4 and SC/Ni3Sn4 interface. The SZ solder reacted with the Ni3Sn4 phase to form the Ni5(Zn, Sn)21 phase at the interface. And then Zn atom diffused toward the Ni3Sn4 phase to form the Ni3(Sn,Zn)4 phase.