The traditional network is unsuitable for continuously increasing requirements and dynamics of users and applications. It is becoming the main bottleneck to any further advancement. The recently proposed concept of cognitive network appears as a candidate that can address this issue. First, we introduce the related background of cognitive network, include: definition, Functionality and cognitive framework. Next, we analyze some research challenge for cognitive network on this emerging area. Besides, we analyze the possible application prospects and finally we close with the conclusions.