Abstract: Lid-driven cavity flow is a simple yet classic flow configuration that exhibits rich fluid dynamic characteristics. In this study, the lattice Boltzmann method (LBM) is employed to investigate the flow and mixing behavior of miscible fluids in a lid-driven square cavity, with a particular focus on the effects of the initial proportion of low-viscosity fluid, viscosity ratio (M), and Péclet number (Pe) on the displacement and mixing process. The results show that increasing the initial proportion of low-viscosity fluid and the viscosity ratio M delays the stabilization of the flow field but has little effect on the steady-state velocity and concentration distributions. A higher initial proportion of low-viscosity fluid leads to a higher steady-state concentration, whereas a larger viscosity ratio M results in a lower steady-state concentration. Additionally, as Pe increases, the mixing process in the cavity is suppressed, and the flow field stabilizes more quickly. At low Pe, the concentration field transitions from a typical triangular distribution to a circular one.