The invention provides a separation method of a chlorosilane mixture, and mainly solves the problems of long flow, great investment, high energy consumption, and the like of a chlorosilane rectification separation process in current polysilicon production. The method of the invention mainly comprises the following steps: adding raw materials of a chlorosilane mixture of dichlorosilane, silicon tetrachloride, and trichlorosilane into a material charging side of a dividing-wall section of a dividing-wall rectifying column, performing separation to obtain trichlorosilane from an extraction side of the dividing-wall section, to obtain dichlorosilane from the column top, and to obtain silicon tetrachloride from the column bottom. The separation method of the chlorosilane mixture of the invention applies the dividing-wall rectification technology to chlorosilane rectification so as to realize complete thermal coupling in the column, saves energy consumption by about 30% when compared with a routine chlorosilane rectification flow, shortens the flow, reduces equipment investment, and saves land occupation.