In order to ensure that the power system operate safely and reliably, and make the fault detection on real-time. According to the study on the noise of different changes of weak signal, We put forward a model of DUFFING chaotic detection for weak signal. When The system is failure,it occurs the corresponding weak signal, through the DUFFING chaotic oscillator method to analyse time domain waveform of weak signal,which under different conditions and phase plane trajectory variation. Then establish the corresponding detection mathematical model, and simulate the amplitude of chaotic detection. The results show that when r=0.8264V, w=1rad/s, then add white noise and weak sinusoidal signal at the same time, the phase plane trajectory of chaotic state and large scale periodic state is still in regular operation, which can clearly observe the detected signals. If there is the the strong noise in the system, this method will overcome the interference of noise to signal stability, will accurately and effectively detect weak signals. When the system response to different working environment and equipment aging situation, The method improve the weak signal detection efficiency and ensure stable operation of the system.