One of the major concerns in the whole lifetime of aircraft composite structures is their susceptibility to impact damage. Aiming at the impact monitoring of large scale composite structures, this paper puts forward an on-line wireless impact monitoring system based on a kind of wireless digital impact monitor developed. Different from traditional processing methods, the new one is fulfilled in a digital way by turning the outputs of PZT sensors directly into digital queues and localizing the impact occurring sub-region based on the digital queues obtained. Meanwhile, validation experiments are implemented on an unmanned aerial vehicle (UAV) composite wing. The results show promising performance of the proposed system for on-line structural health monitoring (SHM) applications on large scale aircraft composite structures.