The invention provides a space vector modulation method of a nine-switch converter. The space vector modulation method of the nine-switch converter includes the steps of determining hexagons where tworeference voltage vectors are located by using the original values of the reference voltages of upper and lower AC terminals; respectively differentiating the two reference voltage vectors from the center vectors of the hexagons where they are located, converting the two reference voltage vectors from a nine-switch converter voltage space vector plane to a six-switch converter voltage vector space plane, selecting six-switch converter equivalent voltage vectors, and determining the action time of the equivalent voltage vectors; mapping the six-switch converter voltage vectors into a nine-switch converter voltage vector plane, and at the same time, converting the action time of the six-switch converter voltage vectors into the action time of the nine-switch converter voltage vectors. The space vector modulation method of the nine-switch converter has the advantages that the method is easy to understand, the complexity of the modulation method of the nine-switch converter is simplified,digital implementation is facilitated, and the method helps to understand the working mechanism of the nine-switch converter and has important practical value for the application of the nine-switch converter.