Abstract: The local delay is an important indicator to evaluate the performance of wireless communications. Yet very little research has focused on the local delay in Cognitive Radio (CR) networks. In this study, CR local delay is defined when secondary nodes opportunistically access the licensed channel. According to the property of omega function, an equation and approximate method are proposed to derive the closed form expression of CR local delay. Numerical results show that the approximate value had the same property as the definite CR local delay on some parameters and was meaningful for the further analysis of CR local delay.