The invention provides a preparation method of yakwool yarns. The preparation method comprises the following steps: mixing yakwool with a health maintaining auxiliary and then covering tightly to obtain health maintaining yakwool; mixing the health maintaining yakwool with water-soluble fiber and then carding to obtain a mixture card sliver; drawing the mixture card silver to obtain fiber drawn sliver; roving the fiber drawn sliver to obtain rough yarn; performing fine spinning of the rough yarn to obtain one-ply yarn; doubling multiple one-ply yarns to obtain plied yarns; twisting the plied yarns to obtain a finished product of yarn; and washing the finished product of yarn to obtain yakwool yarns. In the preparation method provided by the invention, the doping fiber added in a spinning process can be removed to obtain pure yakwool fiber. Moreover, by adding and removing water-soluble fiber in the middle process, the count of the yakwool fiber can be increased.