This paper proposes a space vector pulse width modulation (SVPWM) algorithm with high expansibility and low computational complexity for multilevel inverters. Firstly, this paper presents a new two-level SVPWM algorithm based on virtual time, with a unified calculation method to determine the action time of the basic voltage vector. This algorithm can avoid regional judgment, reducing the amount of computation. Then, the implementation of the proposed multilevel SVPWM algorithm is introduced in detail. By decomposing the reference vector into multilevel basic vector and two level reference vector, the synthesis of voltage vector in multilevel space is transformed to two level space. The complexity of generating the sequence of multilevel basic vector and calculating its time of action has nothing to do with the specific level of the inverter. The effectiveness of the proposed method is proved by the PSCAD simulation of a three-phase five level NPC/H bridge inverter and the experiment of the three-level NPC inverter.