Abstract: Aimed at a composite fault of rotor failure and weak roller bearing fault, a fault diagnosis method based on empirical mode decomposition (EMD) was proposed to separate the coupling features of the composite fault and to extract the fault feature of the roller bearing. Signals were decomposed to obtain several intrinsic mode functions (IMF) by EMD. Main components are confirmed by calculating the correlation coefficient of every IMF and original composite signal, and false components were removed at the same time. Finally low-frequency rotor fault feature was extracted by FFT from the low-frequency component of main components, and high-frequency modulate feature of the roller bearing was extracted by Hilbert envelope demodulation from the high-frequency component of main components. Simulation and experiment analysis results indicate the validity and the practicability of the method proposed.