Weak fault signal not only refers to the signal with very small amplitude, but also refers to the signal existing in the background of strong noise. Weak signal detection technology is widely used in communication, radar, magnetism, vibration measurement, medicine and other research fields. Based on the essence of chaos, this paper summarizes the research status of chaos at home and abroad, including the basic characteristics of chaos system, the basic characteristics of chaos, the chaotic dynamics model and the discriminant method of chaos. The different methods of chaotic weak fault feature extraction are analyzed, their advantages and disadvantages are pointed out, and the research trend is forecasted