The mechanism of bubble capture in a vortical flow is investigated using a Lagrangian bubble tracking method. The motion of bubbles and the factors influencing their movement are examined. Detailed analysis is conducted on the roles played by each force component, such as the lift, added mass, and centrifugal forces, in the bubble capture process. An interesting finding is the identification of the stabilizing effect of the azimuthal lift force on the bubble capture mechanism. Furthermore, a model for capture time based on the radial force balance is also developed, and validated with existing experimental data. These findings, including the force mechanism and capture time model, provide a foundation for understanding the bubble capture process and can potentially inform future studies on tip vortex cavitation inception such as determining the cavitation hotspot.