This paper first derived the function between the transmission time and the interference for given Bayesian risk value. On this basis, the following two interference constraint algorithms were proposed, i.e., the non-cooperative sensing mode frame length design algorithm to maximize system throughput and the cooperative sensing mode frame length design algorithm based on Newman-Pearson criterion. Simulations results have shown that, even if the Bayesian risk value is large, the proposed algorithm can achieved better throughput due to the optimization of the frame length, compared with the existing schemes.