Abstract: We carry on experimental study about law and mechanisms of electromagnetic radiation (EMR) from coal measures rock with precrack during its failure under uniaxial compression in the article. The results show that the presence of precrack in rock samples reduce the intensity and the pulse number of EMR signals; the intensity of EMR from the rock sample with 30° prepared crack during its failure is lower than that of 45° prepared crack; EMR signals from rock samples with precrack during their failure has wave and phase properties; the principal mechanisms of EMR generation during loaded coal measures rock failure are also different for different inclinations of precrack.