In order to study the overall fatigue performance of the original pavement with asphalt mixture overlayer， composite small beams were prepared by adding SMA-13 asphalt mixture over AC-16 asphalt mixture simulating the original pavement. The bending experiments were conducted and the mesoscopic scale analysis of different layers of the composite small beams was carried out using the digital image correlation（DIC） technique. The results show that the fatigue life of composite small beams is negatively correlated with the experimental temperature， stress ratio， and degree of aging. The original pavement is the main part to resist the load， and the overlayer improve mainly the functionality of the pavement. The fatigue cracking process of composite small beams can be divided into three stages， which are the initial damage stage， the damage development stage， and the damage destruction stage.