The work aimed to study the effect of microarc oxidation (MAO) surface treatment on the high temperature steam oxidation behavior of pure zirconium. The oxidation resistance of pure Zr with and without a MAO ceramic coating of about 2.5 μm thick in 1000~1200 ℃ steam environment was evaluated by a thermogravimetric analyzer (TGA). The microstructures and phase components of bare and MAO-coated Zr before and after steam oxidation were analyzed. Their composition depth profiles of Zr, O, P, Na, C, and H elements before and after steam oxidation test were carried out by glow discharge optical emission spectroscopy (GDOES). It was found that their kinetic transition temperature for accelerated oxidation was about 600 ℃ in water vapor environment. The mass gain of MAO-coated pure Zr was lower than that of bare Zr after 3600 s steam oxidation at 1000 ℃, however, their oxidation kinetics curves almost overlapped at 1100 ℃ and 1200 ℃. In the initial stage of steam oxidation, oxygen atoms diffused rapidly into β-Zr substrate. When the thick α-Zr(O) layer and ZrO2 layer were formed, the oxidation rate of bare and MAO-coated Zr was mainly governed by the oxygen diffusion rate in α-Zr(O) layer. Furthermore, the zirconia layer prevented from hydrogen pickup into Zr substrate. After high temperature steam oxidation, the oxide layers of both bare and MAO coated pure Zr consisted of monoclinic zirconia (M-ZrO2) and a little tetragonal zirconia (T-ZrO2) phases. The MAO coating enhanced the steam oxidation resistance of pure Zr below 1000 ℃, but not above 1100 ℃.