Abstract: The high-pressure boiler steel 12Cr1MoVG was produced in steelmaking plant,TPCO,by using foaming slag submerged arc operation in the whole period of EAF steelmaking,EBT tapping alloying,LF compound refining slag,Ca-Si wire feeding after VD treatment and casting with shielding practice.The quantity and changes of total oxygen,microinclusions and macroinclusions in the liquid steel in different steps were stud-ied by the way of sampling systematically,tracers and comprehensive analyses.The results show that the TO is 15×10^-6 after LF/VD refining and 17×10^-6 in tundish,and the TO of cast billets was 18×10^-6~24×10^-6.The number of microinclusions was 3.53 mm^-2 with sizes less than 10 μm,which were mainly spherical calcium alu-minate,aluminosilicate and compound inclusions of aluminate and sulphide.The macroinclusions were mainly ferrum-aluminum silicate,magnesium-calcium silicate,etc.The macrostructure is uniform and the surface quality is good.Each technical index meets the requirement of GB5310 standard.