Sn is one of the main interconnect materials for transient liquid phase bonding of 3D packaging chip stacking.The results show that Ti nanoparticles can improve the wetting spreading area of Sn paste on the surface of copper substrate and significantly increase the tensile force and shear force of Sn solder joint, but excessive Ti nanoparticles would deteriorate the mechanical properties of solder joint. Based on the content optimization of Ti nanoparticles, it is confirmed that the optimal addition amount of Ti nanoparticles is about 0.1wt.%. Analysis of Cu/Sn/Cu and Cu/Sn-0.1 Ti/Cu 3D packaging samples reveales that the thickness of Cu/Sn-0.1 Ti/Cu solder joint intermetallic compound is significantly lower than that of Cu/Sn/Cu, confirming that 0.1wt.% could significantly reduce the growth rate of intermetallic compound. Based on the finite element simulation, it is found that 0.1wt.%Ti can significantly reduce the stress-strain of solder joint in 3D packaging and improve the reliability of 3D interconnect joint.