Abstract: The wavelet packet transform (WPT) method was proposed to denoise for the measured wave in the impulse current test. The four denoising methods, including the WPT method, the Fourier transform, the curve fitting and the wavelet transform method, were used to denoise for the same waveform with noise. Also, the denoised waveform parameters were calculated. The research indicates that the noise frequency has no impact on the denoising results. The error of waveform parameters denoised with WPT is the least. The influence on the wave front is little and the magnitude of denoised wave is almost the same with the standard wave. On the contrary, the error of denoised wave with curve fitting is the maximal. The investigation on the measured wave verifies that WPT is the most precise and practical method.