The invention discloses a control method of a six-phase alternating current motor; the control method comprises the following steps that current given values and current feedback values of a d-axis and a q-axis of each set of winding are determined; a direct-current power supply voltage value of each converter module is determined; the voltage control components of each set of winding are calculated according to the current given values and the current feedback values by adopting a preset control algorithm; a preset decoupling expression is adopted, the voltage decoupling quantity comprising an internal decoupling term of the winding and a cross decoupling term between the two sets of windings is calculated according to the current feedback values; the voltage control component and the voltage decoupling quantity are summed to calculate the voltage control total quantity; and according to the voltage control total quantity and the direct current power supply voltage value of each set of winding, spatial vector modulation is carried out to generate pulse control signals, and the pulse control signals are sent to converter modules corresponding to each set of windings respectively. According to the method, the winding current can be comprehensively and effectively decoupled, so that the control performance is effectively improved. The invention further discloses a six-phase alternating current motor system and a control device thereof, and also has the beneficial effects.