A magneto-optical current sensor based on Bi₄Ge₃O₁₂ (BGO) crystal is proposed in this paper.The sensor which adapts polarimetric detection scheme is used to measure 8/20μs im pulse current whose amplitude is in the range from 10kA to 90kA. Compared with the variation of light source in tensity,impulse current duration time is very short and the measurement disturbance caused by light source is neg ligible.Thus,polarimetric current sensing configuration scheme can guarantee the correctness of measurement result s. Since BGO crystal has the prominent advantage of large Verdet constant,the proposed current sensor can ob tain high measurement sensitivity. In order to remove noise effectively,wavelet decomposition method is used as sp ecific denoising technique. According to the signal-to-noise ratio (SNR) and smoot hness (SR) of denoised s ignals,Db7and decomposition level of 5are chosen as appropriate wavelet function and decomposition level,r espectively.Experimental results reveal that sensor has a good linear sensitivity of 0.2622°/ kA and the measurement error of impulse current peak value is within ±5%.The proposed sensor has the advantage of simple and reliab le structure,showing a potential application in impulse current measurement in h arsh environment including lightning current test,nuclear physics experiment and high-power laser pulse research.