The invention belongs to the technical field of electric power system, An on-line identification method of damping coefficient of synchronous generator based on zonal modeling is disclosed, Making full use of the small and medium disturbance data collected by PMU, the flexibility of on-line identification of the damping coefficients of generator sets in each mode is improved, the pre-control ability of low frequency oscillation warning is improved, and the double errors caused by inaccurate parameters of external system model are effectively isolated, so that the validity and accuracy of the identification of damping coefficients of generator sets are improved. It can significantly reduce the scale of unit damping identification and improve the speed of identification.