Abstract: Sn58Bi-0.1Er solder alloys with different Ni-CNTs content were prepared by vacuum melting method, and the effect of different Ni-CNTs content on the wettability of Sn58Bi-0.1Er composite solder on Cu substrate were studied. The interface structure morphology of the intermetallic compound at the joint interface and shear properties under different Ni-CNTs content were analyzed. The results show that when the addition of Ni-CNTs reinforcing particles is 0.01wt% − 0.05wt%, the wettability of the composite solder alloy on the Cu plate is improved, with the further increase of Ni-CNTs content, the wettability of the composite solder on the Cu plate began to show a downward trend. With the addition of Ni-CNTs, the Sn58Bi/Cu interface intermetallic compound transform from serrated Cu₆Sn₅ to thin layered (Cu, Ni)₆Sn₅. The addition of Ni-CNTs reinforcing particles can effectively reduce the thickness of the intermetallic compound layer. The addition of Ni-CNTs reinforced particles improves the shear force of the Sn58Bi/Cu joint. When the addition amount of Ni-CNTs is 0.1%, the maximum shear force of the joint is 432.86 N, which is more than twice the shear force of the Sn58Bi-0.1Er solder joint. The addition of Ni-CNTs reinforced particles effectively improves the mechanical properties of the Sn58Bi-0.1Er joint.