Abstract: Bio-oxidation leaching test was conducted on a low-grade primary gold mine in Inner Mongolia. The acid consumption of ore, cyanidation, bio-oxidation stirred leaching, column leaching, add sulfur and sulfur concentrate to reduce acid consumption , and impact on gold leaching efficiencies were investigated. The results showed that with grinding fineness at -74 μm 80%, acid leaching for 1h, consumption of sulfur acid at 31 kg/t; After cyanidation for 24 h, the gold leaching efficiencies were 51%~55% ; After Bio-oxidation stirring leaching for 6 d, the sulfur oxidation efficiencies was reaching 80%, and the gold leaching efficiencies was reaching 91.4%; Bio-oxidation column leaching tests on gold ore of particle size at -2 mm 80% for 350 d（oxidation 170 d and cyanide leaching 180 d）, the gold leaching efficiencies was increased by 3.72%~23.54% than the direct cyanide leaching 360 d; The addition of sulfur and sulfur concentrate was not conducive to gold cyanide leaching, and the bio-oxidation of sulfur outside the column could reduce the consumption of sulfuric acid by 15.7 kg/t.