In order to simulate the stress-strain curve of unidirectional ceramic matrix composites（CMCs） under fatigue loading， a theoretical model of the fatigue hysteresis curve of unidirectional CMCs with different cycles and different fatigue peaks is developed. The loading process is divided into four stages and the slip zone consists of the new forward slip zone， the old forward slip zone and the reverse slip zone， while the slip zone of the unloading process is divided into the new forward slip zone and the reverse slip zone. The axial stress distribution of the fibres in each region of loading and unloading is analyzed， and the fatigue stress-strain relationships corresponding to the four loading stages and unloading are derived. The fatigue hysteresis curves of unidirectional CMCs are predicted for different peak stresses and different cycles， and the predicted results are in good agreement with the experimental results in the literature.