Abstract: Finite element method was used to study the reliability of soldered joints of QFP device with three kinds of solders. The results indicate that the strain concentration areas in soldered joint locates at the heel and toe of the soldered joint and the area between the lead and soldered joint.Comparing with the simulating results about Sn3.8Ag0.7Cu, Sn9Zn and Sn63Pb37, from the diagrams of equivalent stress curves, it is found that the stress value in the soldered joint with Sn63Pb37 solder is the largest, and the value in the joint with Sn3.8Ag0.7Cu solder is the least.Sn3.8Ag0.7Cu is considered one of the most favorable solder as a lead-free standard alloy for packaging of micro-devices.By analyzing stress diagrams of curves of solder of the two kinds of QFP64 and QFP208 devices, the stress of solder of QFP208 is lower than that of QFP64, so its reliability is better.