Abstract: Selecting appropriate spectrum sensing time and data transmission time to maximize systemic transmission efficiency is a core research region in Cognitive Radio (CR), it has comprehensive application background. In this paper, a cycle transmission optimization mechanism is proposed. In the optimization algorithm, spectrum detection time, channel searching time and data transmission time are derived respectively. Numerical and simulation results show that the obtained optimal spectrum detection time, optimal channel search time and optimal data transmission time can protect primary users right and decrease data transmission delay effectively.