Understanding the motion behaviors of non-metallic inclusions in the liquid metal is important for clean steel production. High-temperature confocal laser scanning microscopy is applied to investigate the effect of different Ti and Al contents on the agglomeration behavior of non-metallic inclusions in low carbon steels. Furthermore, the agglomeration mechanism of inclusions was investigated through quantitative analysis of in-situ observation experiments and a modified Kralchevsky-Paunov model. The obtained results indicate that Al2O3 is the main type inclusion in the low-alloys steels with both Al and Ti addition. This type of inclusion is more likely to absorb surrounding small-size inclusion particles, leading to a further growth for the cluster formation and contributing to a serious engineering problem, nozzle clogging. Besides, TiOx is the main type inclusion in the molten steel with only Ti addition, and this type of inclusion is less likely to agglomerate and the individual inclusion particles show a ‘free’ motion with the fluid of molten steel. The difference between these two types of inclusions is due to the difference in attractive force and action distance at the meniscus created by the inclusion/steel/Ar multiple interfaces and influenced by the physical parameters, e.g., contact angle and interface energy between inclusion and steel, and surface tension of the melt.