In order to study the chaos phenomenon and chaos control of the direct-drive wave power generation system,the permanent magnet linear synchronous machine(PMLSM) system was transformed into similar Lorenz chaotic equation based on the d-q axis model of PMLSM. At some specific operation status and parameters, the chaos motion of PMLSM was proved by calculating the largest Lyapunov exponents spectra. The order of the chaos system was reduced by constructing the state feedback decoupling controller.The sliding mode controller was designed according to the virtual control quantity constructed by backstepping method. The backstepping sliding mode control strategy was proposed to realize chaos control of PMLSM with constructing control law.The global unanimous asymptotic stability of the PMLSM system was proved via Lyapunov stability analysis.The simulation results show that the proposed backstepping sliding mode controller can inhibit the chattering of traditional sliding control method with preserving the strong robustness of sliding mode variable structure.The PMLSM can quickly escape from the chaotic state with a certain advantage by the control method.