Abstract: In view of problem that conversion efficiency of rotator flux of brushless doubly-fed machine influences on working efficiency, the paper proposed an optimal design scheme of non-salient pole rotator structure of brushless doubly-fed machine. It made optimal design for non-salient pole rotators with less function, namely changing theirs groove to half open-slot and changing theirs length-width ratio constantly; it used finite element software ANSYS to analyze brushless doubly-fed machine with non-salient pole under different length-width ratio rotators structure to gain distribution of excitation of power winding and control winding; it used Matlab software to decompose magnetomotive force of rotator to gain harmonic content of magnetomotive force of rotator, so as to determine the most effective harmonic content. The experiment result showed that brushless doubly-fed machine with non-salient pole has the best energy conversion efficiency at rotator structure with 15 times length-width ratio when setting length-width ratio of non-salient pole is 10, 13, 15, 17 and 20 respectively.