This　article　presents　a　quick　approach　to　measure　the　thermal　resistance　of　PCB　in　vacuum　based　on　the　relationship　of　temperature　and　Schottky　junction　voltage　drop.　Once　the　steady　heating　curve　of　SiC　diode　is　obtained,　the　temperature　characteristic　of　small　current　is　applied　to　determine　the　thermal　resistance　of　PCB.　The　transfer　heat　performance　of　PCB　at　different　coverage　Cu　and　different　thermal　via　diameter　is　studied.　The　results　show　that　the　thermal　resistance　of　PCB　is　found　to　decrease　with　the　increasing　coverage　Cu.　Thermal　via　placed　on　the　PCB　is　significant　to　reduce　the　thermal　resistance　of　PCB　under　constant　coverage　Cu.　And　the　thermal　resistance　of　PCB　reduces　with　the　increasing　thermal　via　diameter.　The　finite　element　ANSYS　software　simulates　the　PCB　temperature.　The　PCB　temperature　is　consistent　with　the　experimental　results.