The changing laws of electromagnetic emission (EME) and acoustic emission (AE) during the deformation and failure of the coal or rock sample under uniaxial compression are studied experimentally. Then the energy transformation relation between EME signal and stress fields in the course of deformation and failure of the coal or rock is researched on the basis of experimental testing results. The research results show that: the intensities and pulse of EME and AE will increase with the increasing of loading time or stress and the enhancement of deformation and fracture; the relation between the EME intensity

pulse numbers and the loading stress is positive; the EME value will decrease after the summit value; the changing curve between EME energy and mechanical energy is consistent with the relation curve between stress and strain

which conforms to thrice multinomial approximately; so it is feasible to study the relation between EME and stress during deformation and fracture in view of energy transformation.