Particulate　size　has　significant　influenced　on　the　mechanical　properties　of　particle-reinforced　composite　solder　joints.　In　this　current　research,　Cu　or　Ni　reinforcement　particles　were　mechanically　added　to　the　Sn-3.5Ag　eutectic　solder,　and　the　effects　of　the　particle　size　on　the　mechanical　properties　of　particle-reinforced　composite　solder　joint　were　systematically　studied.　This　investigation　touched　on　how　mechanical　properties　of　the　solder　joints　are　affected　by　particles　size.　A　quantitative　formula　was　set　up　to　correlate　the　mechanical　property　of　the　solder　joint　with　particle　size　in　different　processing　conditions.　Besides,　the　fracture　mechanism　of　the　composite　solder　joint　was　analyzed.