Abstract: Engine power was detected using the cylinder-head vibration signal. Based on the virtual instrument system constructed by using LabVIEW, the cylinder-head vibration signals were detected with accelerometer while the engine was rapidly accelerated from idle speed to high speed, the spectral analysis of the idle and high speed section vibration signals was also made, then low-frequency vibration signal and the impulse signal measured in engine running state were compared and analyzed. The result shows that the low-frequency vibration signal cycle of cylinder-head vibration accelerating signal has a corresponding relationship with the rotation cycle of the engine. And the rotating speed of the engine can be separated from the peak value points of the low-frequency vibration signal, and then the virtual power values at different rotating speeds can be educed with the principle of angular acceleration measurement under unloaded conditions. Therefore the approach to detect engine power by means of cylinder-head vibration signal is proved to be both effective and feasible.