Abstract:The focus in the search for early warning indicators has been concentrated on observation of seismic events prior to the fall. These precursors have been studied to some extension,but none is fully successful. A new method to evaluate roof stability is put forward based on electromagnetic emission(EME) technology. It is known that wide frequent EME signals can be produced in the processes of deformation and failure of coal and rock. EME of coal and rock is a kind of phenomenon during the deformation and fracture processes of loaded coal and rock;and the EME signal becomes stronger with the increases of the velocity rates of deformation and fracture. The amplitude of EME is mainly affected by the intensity of load and the extent of deformation and fracture;and the impulse number is mainly influenced by the rate of deformation and microfracture. The EME technology has been applied to monitor the hazard degree of coal and gas outburst and rockburst in mines. By means of EME technology the tunnel stress distribution and stress state in working faces can be also evaluated. So,by means of EME monitoring technology,the stability of mine roof can be evaluated. The excavated work procedure has slender effect on the EME monitoring data. The EME amplitude and fluctuation become distinctively greater in geological structure where the strata stress is high. The EME pulse increases distinctively in the roof instability