Abstract: Fe-Si+CaO composite powder cored wire was added into molten steel, and its effect on the removing inclusions was studied. The results show that the composite powder cored wire can be added into molten steel，in which the composite powder can diffuse into molten steel and form Si-Ca-Al composite inclusions with the inclusions in molten steel. The appearance of composite inclusions is spherical，which is easy to accumulate and float up. The industrial trial results show that，the composite powder cored wire can remove inclusions and purify molten steel without affecting the control of steel composition. The T.O content，area content and number density of inclusions are decreased significantly，and the sizes of inclusions remaining in the slab are mostly less than 4 μm，and no size larger than 10 μm inclusions.

Key words: composite powder cored wire, molten steel purification, removing inclusions, composite inclusions