The invention relates to a calculation method for six-phase synchronous motor-converter system switch frequency current harmonics. The calculation method is characterized by comprising the steps of obtaining a reference voltage vector; determining a synthesis-participated voltage vector and acting time of the voltage vector according to a modulation way; calculating flux linkage ripple within a single interrupt cycle; calculating switch current harmonic effective value square within a single fundamental wave cycle; and calculating a stator single-phase winding switch current harmonic effective value. According to the calculation method, the mathematical analysis formulas of the switch frequency current harmonics under different modulation ways are deduced and analyzed; compared with a conventional simulation experiment for determining the switch frequency current, the calculation method provided by the invention saves plenty of time; in addition, the maximum switch frequency current harmonic value in a whole linear modulation region is determined according to the switch frequency current mathematical analysis formulas and the voltage modulation ratios, so that theoretic foundation for determination of heating characteristics of a motor and determination of parameters of machine side converters and electric reactors are provided.