A novel scheme for ball bearing faults detection is presented based on Hilbert-Huang transformation and its energy spectrum. The basic method is introduced in detail. The energy spectrum is applied in the research of the faults diagnosis for the ball bearing of machine tool. Firstly, the analyzed vibration signals are separated into a series of intrinsic mode function using the empirical mode decomposition. Then, the energy spectrum is applied to the intrinsic mode function. The experimental results show that this method based on Hilbert-Huang transformation and energy spectrum can effectively diagnosis the faults of the ball bearing.