Abstract: The essence of coal and gas outburst disaster is the process of energy evolution to catastrophe. To reveal the energy evolution mechanism of the outburst process, the elastic energy and gas expansion energy of coal and rock specimens with different degrees of damage are tested in this paper. The results show that: when the test piece is loaded, part of the total energy input is converted into elastic energy, and part of it is converted into dissipative energy. The elastic energy at the peak intensity accounts for about 70%, the energy is released after peak intensity, and the elastic energy is sharply reduced;under gas pressure of 0.8 MPa, the gas expansion energy is more than one order of magnitude higher than the coal body elastic energy; peak strength is the point at which elastic energy and gas expansion energy can mutate. The elastic energy at the peak intensity decreases sharply, while the gas expansion energy increases by more than 25%. Since gas expansion energy is the main energy, the impact of this energy mutation on coal and gas outburst is enormous.