The chaos detection method based on Holmes Duffing equation is studied. Since this method is suitable only for the detection of a single signal frequency, the selection of the equation parameters is inconvenient, and the noise may affect the detection results, we propose a new method of detecting weak characteristic signals based on the scale transformation of Duffing oscillator. The numerical simulation shows that the proposed method can be used to detect harmonic signal with any frequency and phase by only a set of determined parameters.