Obtaining the partial discharge（PD） characteristic is one of the key issues of PD ultra-high frequency（UHF） detection. To study the relation between PD pulse current and its UHF signal is helpful to the insulation diagnosis. According to the theory of electromagnetic radiation， the radiating field of the PD pulse current under the influence of the metallic tank shell is deduced and its transverse electromagnetic wave characteristic is analyzed in this paper. Based on the above， a new method for deducing PD pulse currents with the time integral of its radiating UHF signals is presented， and the influence of UHF measuring system frequency bandwidth on the algorithm is also discussed. Simulation results and the typical needle-board discharge experiment show that the proposed method can effectively estimate the PD pulse shape and is of value for on-line monitoring and intelligent diagnosis of UHF PD in power transformers.