To solve the problem of multiple noises existing in wind farms which affect the partial discharge (PD) online monitoring results of oil immersed transformers,a partial discharge online monitoring and analysis method for the transformers in wind farms based on the ultra high frequency (UHF) technology was put forward and the design of the UHF PD sensor and frequency reduction circuit of its supporting hardware was made.The UHF partial discharge monitoring and analysis model for the transformers,including their hardware framework and software construction scheme was built.The method was verified by the measured signals in a certain wind farm,which proves that the method proposed can effectively avoid electromagnetic interference,obtain reliable real partial discharge pulse,and realize the fault diagnosis for transformers in wind farms.