Micro-properties of the oxide scale and near-surface zone of a type 316 steel annealed in air and vacuum have been systematically investigated. Microstructures of the specimens have been examined using optical microscopy and scanning and transmission electron microscopy (TEM). Chemical compositions for the oxide scale and near surface zone were also analysed. The results obtained show that the oxide scale developed in vacuum exhibits a distinct structure from that developed in air. Comparing to the vacuum-developed scale, the air-developed scale possesses a more complicated structure and relatively poor adhesion to the matrix. TEM observations reveal a difference in the dislocation density in the vicinity of the free surface, near-surface zone and the core of the specimens examined. Micro-properties of the oxide scale and near-surface zone of a type 316 steel annealed in air and vacuum have been systematically investigated. Microstructures of the specimens have been examined using optical microscopy and scanning and transmission electron microscopy (TEM). Chemical compositions the results obtained show that the oxide scale developed in vacuum exhibits a distinct structure from that developed in air. Comparing to the vacuum-developed scale, the air-developed scale possesses a more complicated structure and comparative poor adhesion to the matrix. TEM observations reveal a difference in the dislocation density in the vicinity of the free surface, near-surface zone and the core of the specimens examined.