It is imperative test item to winding deformation detection of ultra/extra high voltage (UHV/EHV) equipment, including power transformers and reactor,and its traditional offline work confines undoubtedly the state evaluation of power equipment mainly supported by the signals from live detection/online monitoring. The live detection/online monitoring way is anticipated to the condition state of 750kV transformers/reactors in Xinjiang power grid. The coupling capacity rings and insulated sets are installed on the bottom of two bushings for an exciting input signal of nanosecond pulse and a detecting response signal, to construct a characteristic curve required by defect diagnosis. This simulation was demonstrated for this idea to discuss the feasibility of the proposed method, and the nanosecond pulse coupling ring and insolated set were developed to realize 3 tests with different voltages for the actual 750kV reactor in Xinjiang WuBei substation. All results show that it is technically viable to the live detection of winding deformation faults of EHV/UHV equipment by the live detection method based on nanosecond pulses. .