Abstract. The damage behaviour of a type of layer-to-layer interlock 3D woven composite loaded under quasi-static uniaxial tension is studied in this paper. Based on the experimental result obtained, it can be concluded that the development of inter-yarn cracks between warp yarns and the development of through-the-thickness transverse cracks had caused the nonlinear stress-strain responses for loading cases in warp and weft directions respectively. The experimental result provided here may serve as a good reference, based on which a corresponding material damage model may be devised for this type of composite material.