Ortho-olefination of arenes was achieved with removable 1,2,3-triazole auxiliary through Pd-catalyzed C-H activation. Excellent yields were received even when molecular O2 (1 atm) was used as the terminal oxidant. Other heterocyclic directing groups, such as pyridine and quinoline, gave poor reactivity under this aerobic oxidative condition, which highlighted the unique reactivity of triazole in promoting directed C-H activation.