The invention provides a detection circuit of switch magnetic resistance motor winding voltage and a detection method thereof, belonging to the electromechanical switch magnetic resistance motor field, and especially relating to a circuit for carrying out switch magnetic resistance motor winding instantaneous voltage detection without using a voltage sensor and a detection method thereof. The detection circuit detects direct current bus voltage of a circuit detection power converter through a direct current bus voltage detection circuit, and discriminates a work state of a winding of a switch magnetic resistance motor through a microcontroller to obtain winding voltage. When the microcontroller discriminates the work state of the winding, help of a level and a three-phase winding current signal of a PWM port is needed. The direct current bus voltage detection circuit is composed of a first order difference amplification circuit and a first order filter circuit. According to the detection circuit and the detection method, the quantity of the detection circuit is reduced, and circuit reliability of a control system is raised. A difference amplification circuit is employed, and a common grounding interference problem is solved. The detection circuit and the detection method have the advantages of small volume, low cost, high precision and the like.