In this paper, the in-phase thermomechanical fatigue hysteresis loops of fiber-reinforced ceramic-matrix composites (CMCs) have been investigated. The relationships between the thermal cyclic temperatures, fiber/matrix interface shear stress, fiber/matrix interface debonding/sliding and the stress/strain hysteresis loops have been established. The effects of fiber volume fraction, fatigue peak stress, matrix cracking space, fiber/matrix interface debonded energy and thermal cyclic temperature range on the in phase thermomechanical fatigue hysteresis loops have been analyzed. The in-phase thermomechanical fatigue hysteresis loops of cross-ply SiC/MAS composite have been predicted for different applied cycle number.