For the inaccurate spectrum and energy measurement of antenna coupled lightning electromagnetic signal,experiment and theory are combined to find an equivalent circuit of antenna receiving lightning electromagnetic wave signals,with the purpose to analyze the spectral energy distribution of lightning and electromagnetic signals,and to propose a method of using broadband antenna to monitor lightning current,as well as estimating the size and trends of the lightning current value by measuring coupled voltage amplitude and energy amplitude of the electromagnetic pulse of lightning radiation sources on the receive antenna.Results show that the antenna with broad band measured by S11 curve can accurately monitor the size of lightning electromagnetic pulse and calculate the value and trends of lightning current.All the experimental results and theoretical analysis conclusions are basically in good agreement,which have guiding significance to the improvement of lightning monitoring,predicting and warning systems and to the measurement and analysis of lightning activity.