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 introduction of H2O2 into HF lixiviant with little dependence on HF concentration. Upon leaching with 1 mol.L-1 HF and 2 mol.L-1 H2O2 for only 0.25 h at 55 degrees C, the MG-Si purity could be upgraded from 99.74% to 99.96%, to 99.99% with further prolonging of leaching duration. The sensitivity sequences of precipitates to each etchant were obtained through revealing the microstructural evolution of MG-Si before and after etching. With the help of Raman spectrometry and transmission electron microscopy, the chemical etching mechanism is discussed.