Abstract: For cognitive radio (CR) networks that consist of multiple secondary TV band device (TVBD) station–user pairs and one primary digital TV (DTV) station-user pair in this article, establishing a cognitive radio network model based on spectrum sharing, analyzing the outage probability of cognitive radio networks based on secondary network selection, and deduce the closed form expression of the interruption probability. Thus, an access scheme for a single sub network is proposed, that is the increase in the distance between the primary digital TV users and the secondary TVBD users reduces the outage probability, and improve the performance of the secondary network access scheme. Finally, simulation verified the theory analyses.