Modular multilevel converters（MMC） are one of the newly developed multilevel converters. The bridge of a MMC consists of several submodules in series with independent DC sources. Combined with characteristics and mechanism of this structure， the space vector states are analyzed， and a generalized space vector pulse width modulation（SVPWM） algorithm for MMC is proposed. The algorithm is based on the optimum synthesis sequence of space vectors. The inherent correlation between multilevel SVPWM and carrier-based PWM was comprehensively analyzed to show that the multilevel SVPWM can be equivalent to proper zero sequence voltage components injected PWM.Through injecting proper zero sequence voltage components into the three phase reference voltages， and rearrange the action time of each voltage vector， 33% of the total switching time can be reduced. The simulation results illustrate the feasibility and validity of the proposed generalized SVPWM and the associated optimization method.