A space vector based synchronous modulation method, comprising: presetting, by a presetting device, a frequency f of a reference voltage vector V ⇀ S, and outputting the reference voltage vector V ⇀ S to a microprocessor; sampling, by the microprocessor, the frequency f of the reference voltage vector V ⇀ S, and retrieving a carrier wave ratio N from a relationship table of frequencies and carrier wave ratios by using the frequency f, wherein the carrier wave ratio N represents a ratio between a switching frequency of an inverter and the frequency f of the reference voltage vector; deriving, by the microprocessor, an angle Δ θ that the reference voltage vector V ⇀ S has undergone from Δ θ = 2 π / N and a modulation angle θ m of the reference voltage vector V ⇀ S from θ m = ( N th - 1) × Δ θ, wherein N th represents the N th sampling; retrieving, by the microprocessor, a modulation ratio m from a modulation ratio vs. frequency graph, wherein the modulation ratio m represents a ratio between an amplitude of the reference voltage vector and a direct voltage; calculating, by the microprocessor, output angles of three fundamental voltage vectors V ⇀ 1, V ⇀ 2, V ⇀ null synthesizing the reference voltage vector V ⇀ S from the modulation angle θ m of the reference voltage vector V ⇀ S, the undergone angle Δ θ and the modulation ratio m; and comparing, by the microprocessor, a variation Δ θ of the angle θ of the reference voltage vector V ⇀ S with the output angles of the three fundamental voltage vectors V ⇀ 1, V ⇀ 2, V ⇀ null, and outputting the fundamental voltage vectors V ⇀ 1, V ⇀ 2, V ⇀ null in response to a comparison result, to control switch statuses of power electronic devices; converting, by the inverter, the direct voltage into three-phase alternating voltages in response to the switch statuses of the power electronic devices (D1-D6); and transporting, by the inverter, the three-phase alternating voltages to an AC motor. presetting, by a presetting device, a frequency f of a reference voltage vector V ⇀ S, and outputting the reference voltage vector V ⇀ S to a microprocessor; sampling, by the microprocessor, the frequency f of the reference voltage vector V ⇀ S, and retrieving a carrier wave ratio N from a relationship table of frequencies and carrier wave ratios by using the frequency f, wherein the carrier wave ratio N represents a ratio between a switching frequency of an inverter and the frequency f of the reference voltage vector; deriving, by the microprocessor, an angle Δ θ that the reference voltage vector V ⇀ S has undergone from Δ θ = 2 π / N and a modulation angle θ m of the reference voltage vector V ⇀ S from θ m = ( N th - 1) × Δ θ, wherein N th represents the N th sampling; retrieving, by the microprocessor, a modulation ratio m from a modulation ratio vs. frequency graph, wherein the modulation ratio m represents a ratio between an amplitude of the reference voltage vector and a direct voltage; calculating, by the microprocessor, output angles of three fundamental voltage vectors V ⇀ 1, V ⇀ 2, V ⇀ null synthesizing the reference voltage vector V ⇀ S from the modulation angle θ m of the reference voltage vector V ⇀ S, the undergone angle Δ θ and the modulation ratio m; and comparing, by the microprocessor, a variation Δ θ of the angle θ of the reference voltage vector V ⇀ S with the output angles of the three fundamental voltage vectors V ⇀ 1, V ⇀ 2, V ⇀ null, and outputting the fundamental voltage vectors V ⇀ 1, V ⇀ 2, V ⇀ null in response to a comparison result, to control switch statuses of power electronic devices; converting, by the inverter, the direct voltage into three-phase alternating voltages in response to the switch statuses of the power electronic devices (D1-D6); and transporting, by the inverter, the three-phase alternating voltages to an AC motor.