The optimization of the number of winding turns plays an important role in improving the performance of the motor. A semianalytical method combining analysis and simulation is used to propose a method for optimizing the number of winding turns of the two sets of windings of the brushless doublyfed motor (BDFM). The electromagnetic power and thermal load formulas of the BDFM are analytically deduced, and then a series of turns matching satisfying the maximum power constraints are obtained. Taking the minimum thermal load as the optimization goal to carry out analytical screening and simulation refinement screening, a group of optimal turns matching with the minimum thermal load under the given power constraint is selected. Using this method to optimize the number of turns of the BDFM model in other literatures, the general applicability of the method is verified. Compared with the turn optimization method which completely relies on finite element simulation, this method filters out about three groups of turns quickly through analytical expression. Through the finite element simulation for refinement and screening, the optimal number of turns in the three groups is finally selected. Therefore, the optimization design cycle is greatly shortened and computing resources are saved.