Reinforced　Ag　nanoparticles　were　incorporated　into　Sn-0.7Cu　matrix　composite　solder　by　a　mechanical　means　in　order　to　improve　the　creep　properties　of　the　solder　matrix.　The　creep-rupture　life　was　studied　of　Sn-0.7Cu　solder　joints　and　composite　solder　joints　reinforced　with　Ag　nanoparticles　at　different　temperatures　and　applied　stresses.　Stress　exponents　and　creep　activation　energy　were　calculated　for　Ag　nanoparticle　reinforced　Sn-Cu　matrix　composite　solder　joints　at　different　temperatures　and　stress　levels.　Steady-state　creep　constitutive　equation　of　the　composite　solder　joint　was　established.　Results　show　that　at　different　temperatures　and　stresses,　Ag　nanoparticles　reinforced　Sn-Cu　composite　solder　joints　have　higher　creep　rupture　life　and　creep　activation　energy　than　Sn-0.7Cu　solder　joints.　It　indicates　the　creep　resistance　of　the　composite　solder　joint　with　1　vol%　Ag　reinforcement　addition　is　better　than　that　of　Sn-0.7Cu　solder　joint.