Abstract:The phenomenon of electromagnetic emission(EME) is caused during the deformation and failure processes of rock and coal. The experiments for seven types of rocks and coals such as hard coal,soft coal,concrete and so on collected from different collieries have been studied in the laboratories. The experimental results show that the EME strength is closely related to the rock and coal stress state. It usually increases with the stress increasing during the pre-peaking phase. The EME strength becomes most powerful when the stress level is 85%–95% during the pre-peaking phase. However,the EME strength rises firstly and then falls with the stress decreasing gradually during the post-peaking phase. During the post-peaking phase,the EME strength comes to the maximum value when the stress level is about 60% during the post-peaking phase,then falls with the stress deceasing. The EME index of rock burst tendency can be defined as the ratio of EME strength in post-peaking phase and that in the pre-peaking phase. It includes two indexes,namely,EME energy index and EME pulse index of rock burst tendency. Both the EME indexes have closely linear relation with the index of rock burst tendency used at present,i.e. the higher both the EME indexes are,the more the liability of rock burst is. It can be used as an EME index to evaluate the liability of coal and rock burst. The classifications of the two indexes for evaluating the liability of rock burst have been established based on the results of experiments. The EME index becomes an important parameter for the EME method to forecast the rock and coal burst tendency and danger. The research results lay a good foundation for rock and coal burst prevention.