The invention relates to a circular current detection method of a duplex-winding double-speed motor. The winding pole pair quantities of the duplex-winding double-speed motor before conversion and after conversion respectively are P1 and P2; and the circulation detection method comprises the following steps of: a, calculating an interval degree b, and calculating the degree value betai corresponding to an ith pole, wherein betai=gamma+i.a, and i=0,1,......,2P2, gamma is an initial value corresponding to a first pole, and betai is the degree corresponding to the ith pole; c, calculating degree differential value thetai of the ith pole, wherein thetai=betai-M*180 degrees-N*360 degrees, M is 1 or 0, N is an integer larger than or equal to 0, and the numerical value of the degree differential value thetai of the ith pole is smaller than or equal to 360; d, drawing the vector values of the 2P2 thetai in an XY plane on the XY plane; and e, calculating to obtain a pole number combination, the vector sum of which is zero, according to the vector values of the 2P2 degree differential value of thetai in the XY plane. Based on that the calculated vector sum of the differential values is zero, the invention can obtain the value of the corresponding pole number combination and ensure that no circular current is generated on the wiring of the duplex-winding double-speed motor with simple algorithm, convenient operation, safety and reliability.