Wireless Communication is playing a key role in implementing the ubiquitous society. However, due to the increasing wireless and mobile devices occupying the spectrum, the frequency resources are believed to become more and more limited. In order to deal with the problem, coexistence is considered to be a effective method to improve the efficiency of spectrum utilization between several different systems. Here, we utilize the UWB system to realize the coexistence, because it is an ultra wide band system which can co-exist with other narrow band systems. On the other hand, Cognitive Radio technology is an intelligent technology which can sense the spectrum environment and adaptively adjust the parameters for wireless transmission. In this paper, by using Cognitive UWB, the spectrum efficiency of the transmission channels is largely improved; Furthermore, the interference to other systems can be effectively avoided.