The fatigue dislocation structures in cyclically saturated [4 18 41] single-slip-oriented Cu single crystal at different values of plastic strain amplitude pl, as well as their thermal stabilities under annealing at different temperatures for 30 min are studied using the electron channeling contrast (ECC) technique in scanning electron microscopy (SEM). It is found that the dislocation structures, such as veins, PSB ladders, PSB cells, Labyrinths, etc. undergo an obvious process of recovery after annealing at 300 ℃. However, when the annealing temperature is higher than 500℃, those dislocation structures basically disappear, and the recrystallization takes place in all specimens, meanwhile, annealing twins form in most cases. The occurrence of the recrystallization and the formation of annealing twins are related not only to the annealing temperature and applied pl, but also closely to the accumulative cyclic plastic strain.