Abstract: Traditional digital filter method and Birge-Massart threshold wavelet method were used to study the denoisng of lightning transient electrical signals. The mean square error and magnitude error of simulation signals were calculated to compare the denoising effects, and double exponential-decay pulse signals and Gaussian white-noise were composed as the simulating signals. Denoising simulation and measured signals proved that the Birge-Massart threshold wavelet ways were better than the traditionally used smoothing filter and FIR digital low-pass filter ones. Comparing mean square error and magnitude error with different decomposition orders after simulating signals denoising, it is concluded that wavelet decomposition order in measuring lightning transient electrical signals should be 5 to