The invention discloses a multi-frequency weak signal detection method for detecting the failure of a rotor in the early stage. A related method is adopted to conduct prophase noise removal, and a chaotic oscillator array scanning method is adopted to realize simultaneous detection of a plurality of frequency weak signals represented by the same failure, that is, signals with noise are denoised through related calculation, a related function is sent to the chaotic oscillator array and serves as a part of chaotic system periodic driving force, and the weak periodic signal of a signal to be detected can be detected through the change of chaotic system phase locus. The method improves the signal-to-noise ratio of the signal to be detected, and completes the detection of multi-feature weak signal through identifying the state of Duffing oscillator, namely the change of phase locus pattern. Therefore, the method has the advantages of simplicity, intuition, definite physical significance and high detection signal-to-noise ratio. Furthermore, the method is capable of completing the weak signal detection of a plurality of known frequencies and easy for engineering realization, thereby having greater development potential.