Sub-synchronous oscillation(SSO)occurs more and more frequently in modern power systems because of the wide application of power electronic devices and series compensation equipment. To solve this problem

a fast SSO component extraction method is proposed

which can effectively suppress power frequency components

harmonic components and noise. With the advantages of fast response and small calculation burden

the method proposed makes it possible to realize online SSO measurement and analysis. Based on this

an algorithm for calculating SSO frequency(mode)

amplitude and phase angle online and a method to suppress the SSO component in the process of power frequency phasor measurement are proposed. Simulation examples and actual examples are given to verify the effectiveness of the method. This work is supported by State Grid Corporation of China(No. 5201011400M5).