Systematic molecular dynamics simulations, along with dielectric measurements on poly(vinyl methyl ether)/polystyrene blends, are performed to investigate the topological effect on the effective local concentration Phi(eff) and the segmental dynamics in linear-linear (LLB), ring-ring (RRB), and linear-ring (LRB) miscible blends. Compared with LLB, a larger average value and broader distribution of Phi(eff) are found in RRB, which is attributed to the chain-bending-back effect from the ring closure. In LRB, however, the average value and distribution of Phi(eff) for ring components are found to converge to their linear blend partners, as a consequence of linear-ring penetration. The conformational factor is incorporated into the self-concentration model and modifies Phi(eff). This correction could satisfactorily predict the effective glass transition temperature T-g,T-eff and the segmental dynamics in both simulated and real miscible blends containing ring components.