This paper discusses two sides to oxygen vacancy (Vo) in endurance of Hf0.5Zr0.5O2 ferroelectric films: 1) Vo in the bulk improves the endurance with a strong wake-up effect due to enhancing the formation of tetragonal phase, and 2) Vo at the interface degrades the endurance with easier breakdown. Cutting off the kinetic linkage between two kinds of Vo is a key to the endurance enhancement.