Abstract：The strength，deformation and fatigue damage process of coal samples No.3 from Baodian Colliery under cyclic loading are studied through experiments by MTS 815.03 servo-controlled rock mechanical test system. The results indicate that the coal is more inclined to fatigue breakage than other harder rocks. Under uniaxial cyclic loading，the fatigue failure “threshold value” of coal samples No.3 from Baodian Colliery is smaller than 81% of the uniaxial strength；and there will also be a certain extant of fatigue damage when cyclic loading and unloading experiment are carried out below the fatigue failure “threshold value”. Axial deformation can be divided into three stages：initial deformation，constant velocity deformation and accelerating deformation. Radial deformation can be divided into two stages：stable deformation and accelerating deformation. When radial deformation obviously increases and the deformation resumes only a little while removing the load，the coal is going to break. Under cyclic loading，the fatigue damage process with cyclic loading times of coal reflects the process from compressive close，strain hardening to strain softening，as well as the damage evolvement process.
