Regular methods for detecting partial discharge of transformers include the pulse electric current， the dissolved gas analysis（DGA）， the ultrasound， the radio interference voltage（RIV）， the light detection， the radio frequency， the chemical method， etc. According to the principle of the above methods and the characteristic of ultraviolet ray of corona discharge， a new detection method for discharge of transformers based on ultraviolet pulse detection is proposed. The relationship between corona discharge and ultraviolet ray， as well as the spreading characteristic of ultraviolet ray inside transformers， are analyzed. The detection principle of ultraviolet pulse detection is expounded. A monitoring method to positioning corona discharge inside transformers is put forward. The method of ultraviolet pulse detection is designed and validated by experiments. The results demonstrate that this method can be applied to online monitoring for corona discharge of transformers.