Abstract: In the view of turbine regulating valve′s flow characteristics is easy to cause low frequency oscillation of the power unit. When the linearity of valve′s flow characteristic curve is poor, or the regulating valve operates in the area with unstable flow characteristics, the unit is prone to power oscillation due to load disturbance caused by primary frequency regulation. This paper, the cause of several low frequency oscillation events of units are analyzed, and through the optimization test of valve flow characteristics, the linearity of flow characteristics is improved, and the possibility of low-frequency vibration is effectively reduced.