The　outstanding　corrosion　resistance　of　stainless-steel　is　from　its　passive　oxide.　Environmental　transmission　electron　microscope　was　used　in　a　modern　atomic-scale　in　situ　initial　oxidation　analysis　process　to　reveal　the　microstructural　and　elemental　variation　on　its　breakdown.　An　amorphous　oxide　layer　was　the　main　oxide　when　temperatures　is　lower　than　500　degrees　C,　and　pits　formed　from　500　degrees　C,　and　a　porous　structure　formed　from　700　degrees　C.　The　protective　passive　films　on　the　oxide/alloy　interface　were　damaged　by　priority　structural　oxidation　and　prompted　further　alloy　failure.　The　study　provides　direct　experimental　data　beyond　that　of　traditional　research.