The　avalanche　capability　of　Si　MOSFETs　with　different　power　sizes　is　experimentally　compared　and　analyzed　in　this　paper.　The　variation　of　device　current　and　voltage　during　the　avalanche　of　Si　MOSFET　is　reported.　Use　temperature-sensitive　parameters　to　calculate　the　change　in　junction　temperature　during　the　device　avalanche.　The　comparison　shows　that　in　the　same　package,　the　smaller　RDS(on),　the　better　the　avalanche　capability　of　the　device.　The　avalanche　capability　of　the　device　is　related　to　the　heat　dissipation　capability　of　the　device.　In　tests　with　different　inductance　sizes,　it　is　concluded　that　the　ability　of　the　device　to　dissipate　heat　at　large　inductances　is　the　main　factor　affecting　the　avalanche　tolerance　of　the　device.　©　2022　IEEE.