Abstract: Considering that the traditional Prony algorithm is very difficult to analyze the fast attenuate component of the power system low frequency oscillation mode and the fast attenuate component can be missed easily, an improved method of extracting rapid attenuate signal is proposed which is called Prony segment analysis method based on Givens transform. This method divides the data acquisition time into two periods, and the second period is analyzed firstly to calculate the slow attenuate component, then the first period is analyzed for calculating the fast attenuate component. Numerical example proves that this algorithm can accurately extract fast attenuate component of low frequency oscillation mode, and also makes the slow attenuate component more accurate.