Abstract: Little work has been carried out in assessing the property degradation and damage mechanism of polymer thin films under fatigue loading. In this study, the fatigue life and properties of PI/SiO2 films were determined based on the stress amplitude control method. The variation in damping angle, storage modulus, loss modulus and energy dissipation with increasing fatigue cycles were recorded. Furthermore, based on the fatigue modulus concept, an improved model to predict the fatigue life of polymers and their composites is proposed. The results show that the theoretical prediction agrees well with experimental observations.