The　influence　of　oxygen　content　in　shielding　gas　during　MAG　welding　on　the　type,　size,　quantity,　and　distribution　of　oxide　inclusion　and　the　content　of　residual　austenite,　reversed　austenite　and　impact　toughness　of　00Cr13Ni5Mo　deposited　metal　was　investigated.　It　was　found　that　Si-Mn-O,　Si-Mn-Al-O　composite　oxide　inclusions　were　the　main　reason　for　the　degradation　of　impact　toughness　of　00Cr13Ni5Mo　deposited　metal.　The　oxide　inclusions　in　00Cr13Ni5Mo　deposited　metal　could　inhibit　the　generation　of　reversed　austenite　during　tempering.　With　the　increase　of　oxide　inclusions,　the　content　of　reversed　austenite　decreased.