There exist lots of nonstationary components in cylinder head vibrati o n signal of diesel engine and the cylinder head vibration signal has a low signa l to noise ratio, so the feature of cylinder cover vibration is adopted. The vib ration signals from the cylinder cover in different times are measured and denoi sed using wavelet analysis. The working conditions of the cylinder components ar e determined. The vibration intensity is also obtained and its relationship with the rotary speed of the diesel engine is studied. The result shows that the fea ture extracted from vibration of the cylinder cover could be applied to online control and fault diagnosis of the diesel engine.