In order to solve the Byzantine attack problem in cooperative spectrum sensing, a non-cooperative game-theory approach is proposed to realize an effective Byzantine defense. First, under the framework of the proposed non-cooperative game theory, the pure Byzantine attack strategy and defense strategy in cooperative spectrum sensing are analyzed from the perspective of the Byzantine attacker and network administrator. The cost and benefit of the pure strategy on both sides are defined. Secondly, the mixed attack and defense strategy are also derived. The closed form Nash equilibrium is obtained by the Lemke-Howson algorithm. Furthermore, the impact of the benefit ratio and penalty rate on the dynamic process of the non-cooperative game is analyzed. Numerical simulation results show that the proposed game-theory approach can effectively defend against the Byzantine attack and save the defensive cost.