The effect of adding hydrogen peroxide (H₂O₂) as an oxidizing agent on purifying metallurgical grade silicon (MG-Si) by leaching with hydrofluoric acid (HF) was studied as a function of leaching temperature, particle size, leaching duration and concentration of leaching agents. It was found that the extraction capacity for metallic impurities could be significantly enhanced with introducing H₂O₂ into HF lixiviant showing litter dependence on HF concentration. By leaching with 1 mol· L^-1 HF plus 2 mol· L^-1 H₂O₂ for only 0.25 h at 55 ℃, the MG-Si purity could be upgraded from 99.74% to 99.96%, to 99.99% with further prolonging leaching duration. The sensitivity sequences of precipitates to each etchant were obtained through revealing the micro-structural evolution of MG-Si before and after etching. With the help of Raman spectrometry, it was reasonable that etching silicon starts with first oxidizing reaction by H₂O₂ and then dissolved by HF. Like Si-Si bonds, some Si-F and Si-O bonds could also be found on silicon surface after acid etching with HF plus H₂O₂ etchant. After acid leaching, the zigzag silicon surface had been detected by using transmission electron microscopy analysis and the formation mechanism was further discussed.