<p>Slagging and calcium treatment are commonly used methods to control cleanliness and inclusions in steel. However, the inappropriate slagging and calcium treatment operations resulted in the generation of large-sized inclusions and deterioration of steel cleanliness; meanwhile, changed inclusions from Al₂O₃–SiO₂–MnO type to Al₂O₃–SiO₂–CaO type after the calcium treatment during the production of an H-beam steel. Combining the thermodynamic analysis and industrial trials, measurements including reducing the basicity of refining slag to be less than 2.0 and the Al₂O₃ content in slag to be less than 10&#xa0;wt.% and the cancelation of calcium treatment under the total content less than 15 × 10⁻⁶ have been taken. After optimization, the content of total oxygen in tundish decreased by 24%; meanwhile, inclusions were changed from the Al₂O₃–SiO₂–CaO system to the Al₂O₃–SiO₂–MnO system with a low-melting point and a obvious decrease in the number density, area fraction, and maximum size of inclusions. It has achieved the improvement of steel cleanliness while reducing production costs.</p>