Abstract: The fatigue behaviour of continuous-glass-fibre-mat reinforced polypropylene composites (GMT-PPs) with different interfacial adhesion is investigated by dynamic fatigue tests. The results show that the effect of the interfacial adhesion on the fatigue performance of GMT-PPs is obvious and the improved interfacial adhesion results in an improved fatigue performance. Through the observation of SEM, it is found that the failure modes are different in static tension and dynamic tension for GMT-PPs with strong interfaces. The failure mode of the former is the matrix failure, while that of the latter is the interfacial debonding failure, which means that fatigue loading has a more damaging effect on the interfacial adhesion than on the polymeric matrix. The stronger the interfacial adhesion, the more difficult the interfacial debonding, thus GMT-PPs with well interfacial adhesion has the better the fatigue performance.