Though Bi, Al substituted Dy-iron garnet films for magneto-optical recording prepared by pyrolysis are nanocrystalline, but because the imhomogeneity of grain boundaries, the sizes of the grains are bigger and imhomogeneity, there is a serious problem of media noise in magneto-optical recording. While Bi, Al substituted Dy-iron garnet films for magneto-optical recording with Rb-doping not only decreased the crystallized temperature, but also decreased the grains sizes. The biggest grain size from 100 nm decreased to about 50 nm, average grains size decreased to about 30 nm, and the homogeneity of the grains was improved. The reflecting of the surface increased because of the doped Rb existed on the surface of the films in form of Rb2O condensate filling the surface curves. The signal to noise improved. So Rb-doping can greatly improved the magneto-optical characteristics of Dy-iron garnet films for magneto-optical recording.