NPN-type　small　and　medium　power　switching　transistors　in　3DK　series　are　used　to　conduct　analyses　and　studies　of　accelerating　degradation.　Through　three　group　studies　of　accelerating　degradation　in　different　temperature-humidity　constant　stresses,　the　failure　sensitive　parameters　of　transistors　are　identified　and　the　lifetime　of　samples　is　extrapolated　from　the　performance　degradation　data.　Average　lifetimes　in　three　common　distributions　are　given,　when,　combined　with　the　Hallberg-Peck　temperature-humidity　model,　the　storage　lifetime　of　transistor　samples　in　the　natural　storage　condition　is　extrapolated　between　105-107　h.　According　to　its　definition,　the　accelerating　factor　is　1462　in　100　°C/100%　relative　humidity　(RH)　stress　condition,　and　25　°C/25%　RH　stress　condition.　Finally,　the　degradation　causes　of　performance　parameters　of　the　test　samples　are　analyzed.　The　findings　can　provide　certain　references　for　the　storage　reliability　of　domestic　transistors.©　2014　Chinese　Institute　of　Electronics.