Micro-bulk fatigue testing developed to investigate the fatigue lives and damage mechanisms of Sn–3.0Ag–0.5Cu and Sn–37Pb solder alloys. The fatigue life of micro-bulk solder obeyed Manson–Coffin’s empirical law, and the fatigue ductility exponents were about 0.5 for both Sn–Ag–Cu and Sn–Pb alloys. The fatigue life of Sn–3.0Ag–0.5Cu alloy was 10 times longer than that of Sn–37Pb alloy under symmetrical cycling at 298 K, although fatigue resistance of Sn–3.0Ag–0.5Cu alloy was not very superior under asymmetrical wave and elevated temperature condition. The fatigue crack was developed from extrusion and intrusion of slip band in Sn–3.0Ag–0.5Cu alloy, while the crack was observed at colony boundary and grain boundary in Sn–37Pb alloy. The difference in damage mechanism may affect the susceptibility to fatigue life test condition of reversibility.