Sn-Zn solders have great potential in the field of 3D packaging applications due to the low melting point and low cost. However, there are still some problems prevented the development of Sn–Zn solder. Adding reinforcing particles helps to improve the reliability of solder joints. Cu/Sn-1Zn-xAl/Cu (x = 0, 0.2, 0.4, 0.6, 0.8, 1.0 wt%) solder joints were prepared by transient liquid phase bonding (TLPB) method. The effects of Al particle content on the interfacial microstructure and shear properties of solder joints were studied. The results show that the phases of the interface layer are Cu3(Sn, Zn) and Cu6(Sn, Zn)5. With the increase of Al particle content, the thickness of intermetallic compounds (IMC) layer decreases first and then increases. When the Al content is 0.6 wt%, the minimum value is 4.37μm. The porosity of the solder joints also decreases first and then increases with increasing of the Al particles content. As the increase of Al particles content, the shear strength of solder joints increases first and then decreases. The shear strength of Cu/Sn-1Zn/Cu solder joint is 12.51 MPa. With adding 0.6 wt% Al particles, the shear strength of the Cu/Sn-1Zn-0.6Al/Cu solder joint reached its maximum value of 19.29 MPa, which is 54.20 % higher than that of Cu/Sn-1Zn/Cu solder joint. The fracture mode of Cu/Sn-1Zn-0.6Al/Cu solder joint is ductile-brittle mixed fracture, and the fracture location is at the junction of in-situ reaction zone and interface reaction zone.