In high-quality steel production, the final stage of secondary refining typically involves a ladle holding period to facilitate the flotation and removal of inclusions. This improves the cleanliness of the molten steel. This study investigated the evolution of inclusion number density and area fraction during the ladle holding period by conducting industrial experiments on composition adjustment via the sealed argon bubbling refining process of SPHC low-carbon steel. The results indicated that inclusions would be removed by floating during the ladle holding period. The inclusion number density and area fraction decreased from 52.8 #/mm² and 279 × 10^–6 at the start of the holding period to 22.1 #/mm² and 148 × 10^–6 after 15 min, respectively. To clarify the movement and removal of inclusions, a numerical model was developed based on a discrete phase model, incorporating multiphase flow and heat transfer during the ladle holding period. The calculations revealed the following conclusions: (1) inclusions smaller than 10 μm primarily followed the molten steel’s fluid flow, with removal rates of 51.6% and 66.7% after 900 and 1800 s, respectively; (2) inclusions with a diameter of 100 μm were influenced by the molten steel’s fluid flow and their buoyancy, achieving removal rates of 70.2% and 89.2% after 900 and 1800 s, respectively; (3) inclusions with a diameter of 1000 μm primarily underwent flotation, reaching an approximately 100% removal rate after 120 s. This study quantitatively examined the relationship between inclusion removal rates, particle sizes, and refining time during the ladle holding period, thereby providing theoretical guidance for the industrial production of high-quality steel.