It has been proved by field operation that if low-frequency oscillation occurs with turbines，oscillation can be checked by changing the control mode of the speed control system.Literature analysis shows that if the low-frequency power disturbance on the grid side causes mechanical power resonance，the rotor angle amplitude will substantially increase.Hence，by analyzing the damping and frequency characteristics of the turbine control system in serial PI and two kinds of single stage PI control mode，an adjustment strategy is proposed to avoid the resonance frequency.Simulation shows that the amplitude of the rotor can be effectively reduced by turbine control mode adjustment when resonance occurs.This method is of practical significance for ensuring stable operation of the system by quickly checking the low frequency oscillation with the function available of the turbine regulating system on-line.