To investigate the complex flow and vortex structure evolution within the staggered blade centrifugal impeller, Large Eddy Simulation (LES) numerical computation method was employed to capture the unsteady flow field within the impeller flow channel and near the volute togue. Utilizing the Q-criterion vortex identification method, the vortex distribution at two mid-span sections of different impeller schemes was extracted, and the evolution of the vortex structure near the tongue was focused on. The study revealed that staggered blade arrangement generates a large number of multi-scale vortex structures near the inlet flow channel of the posterior blade, dissipating within the flow channel and evolving towards the impeller outlet. The wake vortex band becomes longer and wider as the stagger angle increases. Influenced by both the vortex structures developed within the impeller flow channel and the staggered structures, the shedding time of wake vortices is advanced successively, continuously interfering with the volute togue, resulting in a denser and more complex vortex structure near and downstream of the volute togue.