In next generation of wireless mobile communications, it is demanded that users could visit Internet services through any kind of radio access technology. Monitoring of radio access network (RAN) is very important for reconfigurable terminals (RT) in Mobile Internet. It is the foundation of network cooperation and seamless access for user services. In this paper, a new RAN monitoring scheme based on cognitive radio technology is proposed. RAN information acquisition mechanism is given. RAN monitoring model and reconfiguration platform are present. And the process of signal detection is described. Furthermore, an algorithm on optimal selection of signal detection technologies is designed, where 4 main signal detection technologies are taken into consideration. Finally, taken WPAN monitoring as an example, the availability of this algorithm is proved by simulation results.