In ferrimagnetic media, besides originating from the splitting of the excited state resulting from the spin-orbit interaction, magneto-optical effects also arise from the splitting of the ground state caused by the superexchange interaction and applied field. A theoretical calculation according to this view shows that the Faraday rotation 0 depends linearly on sublattice magnetization Mi (i=1,2,..., l) in both the low-temperature and high-temperature regimes for the medium with high Curie temperature, while in the normal-temperature regime, 0 depends nonlinearly on each Mi and T. The theory is in good agreement with experimental results.