The electric magnetic emission (EME) rules of deformation and failure of composed coal and rock samples are studied by lab experiments and fractal theory. The results show that at the initial stage of loading, EME signals increase, then decline slightly and stay at a stable level. Substantial increase appears when the composed coal and rock samples are close to the main fracture, and EME signals decline slowly when they are in the stage of residual deformation. The EME signals have a positive exponent relation to roof ratio in the composed coal and rock samples. The EME pulse count has the fractal characteristic, and the fractal dimensions increase with the process of loading. When the composed coal and rock samples are close to main fracture, the fractal dimensions decline suddenly, and it has a positive linear relation to the ratio of roof in the composed coal and rock samples. With the achieved rules, the burst danger has been forecasted successfully in face 7251.