The method is suitable for applying a small interference stability online control policy or a set offline policy in controlling practical generated low-frequency oscillation. A low-damping mode of a power grid is obtained by small interference stability calculation; control measures for improving the damping of all low-damping modes to different grades are respectively calculated, and oscillationcenters of all the low-damping modes are confirmed according to the physical characteristics of the oscillation centers; and the power grid is divided into two independent networks in the oscillationcenters. When the power grid generates low-frequency oscillation, a candidate mode set is screened by adopting the frequency in an actual measurement leading mode, a mode corresponding to the actual measurement leading mode is confirmed according to actual measured equipment grouping information, and the corresponding control measure is confirmed according to a difference of the actual measurement leading mode damping and a critical safety damping threshold value. If the mode corresponding to the actual measurement leading mode does not exist, the auxiliary decision information is obtained from an offline policy table. Finally, the corresponding control policy is applied by an automatic generation control (AGC) system or an automatic control system of a power plant.