In this paper, a characteristic signal detection method based on the parameter-tuned resonance of a second-order linear system is proposed. The second-order linear system is taken as a signal detection model, and its resonance characteristics are used to obtain the characteristic curve for describing the change law between the maximal value of system response and the natural frequency. According to the maximum value of the curve, we can identify the characteristic signals from the noise background. Simulation analysis and the experiment of rotor fault diagnosis indicate that the principle of the presented method is simple, and that it may provide a practical method for signal detection and processing.