Abstract: In order to clarify the fluid flow characteristics inside double-fed wind generator,a 1.5 MW double-fed wind generator was taken as an example.According to the structure and cooling type of generators,a multi-dimensional model of fluid-solid coupled for solving the temperature field was established based on fundamental assumptions.By adding boundary conditions,the temperature and fluid fields were analyzed numerically using the finite volume method.And the calculated results were compared with test data,which proved the correctness of the computing method and the solving model.At last the characters of cooling medium（water and air） inner the stator and rotor,such as flow velocity,temperature rise and path lines,were analyzed,which reveals the changing regularity on the performance of cooling medium for large doubly-fed wind generators.