Abstract: With the use of Pb in a variety of occasions prohibited, Lead-free technology becomes one of important research direction. For understanding the fatigue properties of lead-free solder, there is important significance to analyse fanalyse state of lead-free solders and to research on the method of testing. With the 0805 chip capacitor device package solder joints as the research object, Sn96.5/Ag3/Cu0.5 solder joints finite element model is established for multi period under temperature cycles. And shearing test is carried out. The value of Period-shearing stress to Sn96.5/Ag3/Cu0.5 and Sn63/Pb37 solders is obtained. Thermal fatigue fitting curves of solder in 1 500 periods is acquired, by using nonlinear least square method to fit curves. The results indicates that under the stipulated test condition, in limited 1 500 periods, thermal fatigue performance of Sn96.5/Ag₃/Cu0.5 solder joints' rate of thermal fatigue deterioration to 0805 capacitance is slightly slower than that of Sn63/Pb37 solder joints.