To investigate the unresolved influence of grease filling quantity and rotational speed on grease flow distribution in spherical roller bearings under low-speed conditions, a numerical model for grease flow simulation was established. Finite element analysis was conducted based on the Volume of Fluid method and the Multiple Reference Frame approach. The flow behavior and distribution characteristics of grease within the bearing cavity and on component surfaces were systematically investigated under varying grease quantities and rotational speeds. The results demonstrate that during low-speed operation, increased grease filling quantity elevates the mean grease volume fraction within the bearing. The grease primarily accumulates at the outer ring wall and in the cage-inner ring interspace, exhibiting relatively low flow velocities in these regions. In contrast, grease adjacent to rollers and the cage displays higher flow velocities owing to mechanical interactions with moving components, while grease filling quantity variations show insignificant influence on cavity flow velocities. With rising rotational speed, grease redistribution occurs predominantly along the outer raceway and the cage side adjacent to the inner raceway, while simultaneously exhibiting a tendency to migrate toward inter-roller zones within the bearing cavity.