Modal resonance could reveal the mechanism of some low-frequency power oscillation cases in large scale power systems，which could not be well explained by traditional damping torque analysis method. The progress of research and practice on modal resonance studies in the past few decades are reviewed. Firstly，the discovery of modal resonance phenomenon are recalled. Then the theory and experiments of modal-resonance-caused low-frequency power oscillation are concluded. Secondly，the mechanism and hearsay evidence of near strong modal resonance causing low-frequency power oscillation are introduced，including the improvement of the mathematical analysis tools and the suppression measures of the system resonance. Then the engineering examples of resonance in the past decade over the world are given，with the effectiveness of the above mechanism with actual cases. Finally，its theoretic progress，measure improvement and possible application prospect are concluded.