Abstract: Defect sensitivity of the compressive failure modes,as well as the related compressivestrength,of fibre reinforced composites is explored herein by means of the elastic plastic bifurcation theory. It is concluded for the conventional composites reinforced by unidirectional fibres that;failure mode featured by inclined kink bands would prevail if the initial defects inside the composites are small ;on the other hand,failure mode of horizontal bands would be energetically favorable provided the initial damage is substantial,and the resultant critical pressure load for the formation of horizontal band is less than that for in clined band under small initial defect.