The critical fracture energy and failure mechanisms of GF/PP composites are investigated in the temperatures range of the ambient temperature to $-50^{circ}C$ The critical fracture energy increase as fiber volume fraction ratio increased The critical fracture energy shows a maximum at ambient temperature and it tends to decrease as temperature goes up. Major failure mechanisms can be classfied such as fiber matrix debonding, fiber pull-out and/or delamination and matrix deformation.