Abstract: Coal sudden extrusion is a dynamical phenomenon about coal and gas caused by stress, which seriously threatens to the mine safety production due to very little research about its mechanism. The article, taking the first kind of extrusion as research object, on the basis of force analysis, educed the computation formulas of coal compress distortion, displacement and energy in theory. The research result shows that coal compress distortion and displacement increase with the distance to coal wall by exponential law when the first kind of extrusion takes place within the zone of stress limit; in the condition of producing the same maximal displacement, and the deeper of happening location, the bigger of needful energy, and it is also the exponent relation.