The　effects　of　the　delivery　tube　protrusion　on　the　effective　atomizing　efficiency　and　size　distribution　of　the　Sn3Ag2.8Cu　lead-free　solder　powders　were　studied　by　the　supersonic　atomizer　designed　by　ourselves,　and　the　effects　of　alloy　superheat　on　its　effective　atomizing　efficiency　and　properties　were　studied　based　on　the　optimal　delivery　tube　protrusion.　The　results　show　that　the　effective　atomizing　efficiency　of　the　powder　is　not　monotone　trend　with　reducing　the　delivery　tube　protrusion,　two　peak　values　are　respectively　found　at　1mm　and　5mm　of　the　delivery　tube　protrusion,　and　the　powder　has　higher　effective　atomizing　efficiency　and　optimal　size　distribution　at　4mm　of　the　delivery　tube　protrusion,　furthermore　the　delivery　tube　protrusion　can　determine　whether　the　atomizing　process　can　be　finished　successfully;　at　4mm　of　the　delivery　tube　protrusion,　the　size　distribution　of　powder　is　notably　improved　with　increasing　the　alloy　superheat,　but　the　oxygen　content　is　increasing,　the　Sn3Ag2.8Cu　atomized　powder　has　optimal　comprehensive　properties　at　150°C　of　alloy　superheat.