The　solder　paste　has　become　one　of　the　most　indispensable　brazing　and　soldering　materials　in　surface　mount　technology　(SMT),　and　its　performance　affects　the　quality　of　welding　directly.　The　independently-designed　lead-free　solder　paste　in　the　lab　has　the　fine　performance　when　synthesized　initially.　However,　the　performance　of　solder　paste　degraded　during　the　storage.　So　the　aim　of　the　article　is　to　analyze　solder　paste　based　on　performance　degradation.　In　the　paper,　the　independently-designed　Sn-0.3Ag-0.7Cu　solder　paste　in　the　lab　was　compared　with　commercial　Senju　solder　paste　based　on　the　observation　of　wettability　and　viscosity　during　being　stored　at　room　temperature.　Subsequently,　the　solder　paste　was　divided　into　solder　power　and　flux　after　1,3　and　5　months＇　storage.　The　solder　power　was　analyzed　by　scanning　electron　microscopy.　The　results　show　that　during　the　solder　paste　was　sealed　at　room　temperature,　the　wettability　of　solder　paste　became　worse.　And　the　viscosity　was　tend　to　increase,　which　lead　solder　paste　to　become　dry,　sticky,　and　even　fail　in　welding.　In　addition,　solder　powder　would　be　corroded　and　oxidized　during　the　storage.　So　the　activation　component　of　the　solder　paste　reacts　chemically　with　the　solder　powder,　which　results　in　the　performance　degradation　of　solder　paste.