Abstract: This paper investigates continued-time two-dimensional birth-and-death process with priority in cognitive radio system. To simplify analysis, one-dimensional queuing model without priority is derived to equalize the complicated process. And a step-queuing scheme based on channel reward in multichannel scene is proposed, whose block probability and force termination probability performance determined by the Queuing-Structure Coefficient (QSC). Analytical results and simulation confirm the equivalent queuing model without priority valid. Also some diverse access scheme are compared in performance, step-queuing scheme presents a lower block probability and an adaptive force termination probability.