Bio-char reductant was prepared with walnut shells, and characterized to analyze the relationship between chemical components, functional group distribution and resistivity. The results showed that resistivity of bio-char declined from 6288.7 to 1515.9 mW×m with increasing of pyrolysis temperature from 400℃ to 1450℃. Fixed carbon content increased and volatile matter content declined with increasing of pyrolysis temperature. Carbonyl and aliphatic functional groups in the char were gradually decomposed, the interlamellar spacing of d002 on the lattice plane decreased gradually, its crystallinity, aromatization and carbon structure ordering degree increased with increasing of pyrolysis temperature. In the pyrolysis temperature range of 500~700℃, high-performance bio-char reductant with high yield (≥24%), high resistivity (≥5800 mW×m), high fixed carbon content (≥80%) and low ash content (≤4%) was obtained. The char had developed pores, and could be used as the reductant for industrial silicon production.