Studies were conducted on the vapor-phase dehydrofluorination of 2H,3H-decafluoropentane. It was found that 2H,3H-decafluoropentane could be dehydrofluorinated to give Z-1,1,1,2,4,4,5,5,5-nonafluoro-2-pentene and Z-1,1,1,3,4,4,5,5,5-nonafluoro-2-pentene over chromium fluoride or aluminum fluoride catalysts. With stoichiometric calculation, Z-isomer was the main product in the dehydrofluorination owing to its lower relative energy, which was consistent with the experimental result. Consequently, the reaction mechanisms of selective dehydrofluorination of 2H, 3H-decafluoropentane were proposed.