In　the　present　work　the　creep　properties　of　Sn37Pb　and　Sn0.7Cu　based　composite　solders　with　nano-sized　metallic　Cu,　Ag　and　nano-sized　oxide　Al2O3,　TiO2　reinforcement　particles　have　been　studied.　First,　a　series　of　volume　percentages　of　reinforcements　were　selected　for　optimizing　the　content　of　particles.　Then,　the　composite　solder　with　optimum　volume　fraction　of　the　reinforcement　particles,　corresponding　to　maximum　creep　rupture　life,　is　selected　for　investigating　the　effect　of　applied　stress　level　and　test　temperature　on　creep　rupture　life　of　the　composite　solder　joints.　In　the　creep　rupture　life　test,　small　single-lap　tensile-shear　joints　were　adopted.　The　results　indicate　that　all　the　composite　solders　have　improved　creep　resistance,　comparing　to　the　eutectic　Sn37Pb　solder　and　the　Sn0.7Cu　lead-free　solder.　The　creep　rupture　life　of　the　composite　solder　joints　is　first　increased　with　the　increase　in　the　volume　fraction　of　reinforcement　in　the　composite　solders.　Then,　the　creep　rupture　life　is　decreased,　as　the　reinforcement　content　exceeds　a　certain　value.　The　creep　rupture　life　of　the　solder　joints　is　decreased　with　the　increase　of　applied　stress　and　testing　temperature.　Moreover,　the　reinforced　efficiency　of　nano-sized　Ag　particles　is　the　best　in　all　the　tested　nano-sized　reinforcements　for　the　Sn37Pb　based　and　Sn0.7Cu　based　composite　solders,　when　the　particles　contents　are　in　their　own　optimum　content.