Based on the universal method of multi-level SVM， the selection of switching sequences is analyzed and compared for the multi-level SVM and multi-level carrier-based modulation. It is presented that the multi-level SVM can select more switching-sets， which can be used to optimize the output voltage or to balance the DC power. Unfortunately it is complex to achieve multi-level SVPWM， so an improved PWM scheme is proposed in this paper， which is based on the modulation waves of three-level SVM. This proposed method optimizes the output voltage harmonics by adding switches， and can be achieved by a three-level SVM， hence the calculation cost does not increase when the levels increase. Finally， a five-level test circuit is built to verify the PWM scheme.