Dynamic spectrum access (DSA) based on cognitive radios (CR) technique is an effective approach to address the spectrum scarcity issue. However, traditional CR-en-abled DSA system employs only single DSA strategy, which might not be suited to the dynamic network environment. In this paper, we propose a multi-strategy DSA (MS-DSA) system, where the primary and the secondary system share spectrum resources with multiple DSA strategies simultaneously. To analyze the performance of the proposed MS-DSA sys-tem, we model it as a continuous-time Markov chain (CTMC) and derive the expressions to compute the corresponding performance met-rics. Based on this, we define a utility function involving the concs of effective through-put, interference quantity on primary users, and spectrum leasing cost. Two optimization schemes, named as spectrum allocation and false alarm probability selection, are proposed to maximize the utility function. Finally, nu-merical simulations are provided to validate our analysis and demonstrate that the perfor-mance can be significantly improved caused by virtues of the proposed MS-DSA system.