Abstract: According to characteristics that frequency of vibration signals of hoist gear box bearing in coal mine changes all the time under varying load and speed conditions, EMD method was adopted for fault diagnosis for hoist bearing. In phase of larger drag force and greater rotating frequency, working status of bearing is adjusted according to energy ratio and root mean square energy of IMF components of bearing vibration signal under normal status and fault status, and fault position is determined by extracting marginal spectrum of fault signal frequency. The experimental results show EMD method can detect bearing fault of hoist gear box effectively.